diff --git content/browser/renderer_host/render_widget_host_view_base.cc content/browser/renderer_host/render_widget_host_view_base.cc
index f41270e26278..38303c9c3ec8 100644
--- content/browser/renderer_host/render_widget_host_view_base.cc
+++ content/browser/renderer_host/render_widget_host_view_base.cc
@@ -577,6 +577,14 @@ float RenderWidgetHostViewBase::GetDeviceScaleFactor() {
   return screen_info.device_scale_factor;
 }
 
+void RenderWidgetHostViewBase::SetHasExternalParent(bool val) {
+  has_external_parent_ = val;
+}
+
+bool RenderWidgetHostViewBase::HasExternalParent() const {
+  return has_external_parent_;
+}
+
 uint32_t RenderWidgetHostViewBase::RendererFrameNumber() {
   return renderer_frame_number_;
 }
diff --git content/browser/renderer_host/render_widget_host_view_base.h content/browser/renderer_host/render_widget_host_view_base.h
index 8e523d78e765..d951d8915864 100644
--- content/browser/renderer_host/render_widget_host_view_base.h
+++ content/browser/renderer_host/render_widget_host_view_base.h
@@ -71,6 +71,7 @@ class CursorManager;
 class MouseWheelPhaseHandler;
 class RenderWidgetHostImpl;
 class RenderWidgetHostViewBaseObserver;
+class RenderWidgetHostViewGuest;
 class SyntheticGestureTarget;
 class TextInputManager;
 class TouchSelectionControllerClientManager;
@@ -91,6 +92,9 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   float current_device_scale_factor() const {
     return current_device_scale_factor_;
   }
+  void set_current_device_scale_factor(float scale_factor) {
+    current_device_scale_factor_ = scale_factor;
+  }
 
   // Returns the focused RenderWidgetHost inside this |view|'s RWH.
   RenderWidgetHostImpl* GetFocusedWidget() const;
@@ -125,6 +129,8 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   void DisableAutoResize(const gfx::Size& new_size) override;
   bool IsScrollOffsetAtTop() override;
   float GetDeviceScaleFactor() final;
+  void SetHasExternalParent(bool val) override;
+  bool HasExternalParent() const override;
   TouchSelectionControllerClientManager*
   GetTouchSelectionControllerClientManager() override;
   void SetRecordTabSwitchTimeRequest(base::TimeTicks start_time,
@@ -479,6 +485,12 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
   // helps to position the full screen widget on the correct monitor.
   virtual void InitAsFullscreen(RenderWidgetHostView* reference_host_view) = 0;
 
+  // Perform all the initialization steps necessary for this object to represent
+  // the platform widget owned by |guest_view| and embedded in
+  // |parent_host_view|.
+  virtual void InitAsGuest(RenderWidgetHostView* parent_host_view,
+                           RenderWidgetHostViewGuest* guest_view) {}
+
   // Sets the cursor for this view to the one associated with the specified
   // cursor_type.
   virtual void UpdateCursor(const WebCursor& cursor) = 0;
@@ -643,6 +655,10 @@ class CONTENT_EXPORT RenderWidgetHostViewBase
 
   bool is_currently_scrolling_viewport_ = false;
 
+  // True if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent_;
+
  private:
   FRIEND_TEST_ALL_PREFIXES(
       BrowserSideFlingBrowserTest,
diff --git content/browser/renderer_host/render_widget_host_view_event_handler.cc content/browser/renderer_host/render_widget_host_view_event_handler.cc
index 21f93de01aa5..8b7ec41d94da 100644
--- content/browser/renderer_host/render_widget_host_view_event_handler.cc
+++ content/browser/renderer_host/render_widget_host_view_event_handler.cc
@@ -32,6 +32,10 @@
 #include "ui/events/keycodes/dom/dom_code.h"
 #include "ui/touch_selection/touch_selection_controller.h"
 
+#if defined(OS_LINUX)
+#include "ui/aura/window_tree_host.h"
+#endif
+
 #if defined(OS_WIN)
 #include "content/browser/frame_host/render_frame_host_impl.h"
 #include "content/public/common/context_menu_params.h"
@@ -922,6 +926,14 @@ void RenderWidgetHostViewEventHandler::SetKeyboardFocus() {
         ::SetFocus(hwnd);
     }
   }
+#endif
+#if defined(OS_LINUX)
+  if (host_view_->HasExternalParent() &&
+      window_ && window_->delegate()->CanFocus()) {
+    aura::WindowTreeHost* host = window_->GetHost();
+    if (host)
+      host->Show();
+  }
 #endif
   // TODO(wjmaclean): can host_ ever be null?
   if (host_ && set_focus_on_mouse_down_or_key_event_) {
diff --git content/public/browser/render_widget_host_view.h content/public/browser/render_widget_host_view.h
index 07d4351d0a8a..4ad78ab76a7c 100644
--- content/public/browser/render_widget_host_view.h
+++ content/public/browser/render_widget_host_view.h
@@ -246,6 +246,14 @@ class CONTENT_EXPORT RenderWidgetHostView {
   // This must always return the same device scale factor as GetScreenInfo.
   virtual float GetDeviceScaleFactor() = 0;
 
+  // Set whether the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  virtual void SetHasExternalParent(bool val) = 0;
+
+  // Returns true if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  virtual bool HasExternalParent() const = 0;
+
 #if defined(OS_MACOSX)
   // Set the view's active state (i.e., tint state of controls).
   virtual void SetActive(bool active) = 0;
diff --git ui/base/x/x11_window.cc ui/base/x/x11_window.cc
index 7df0a3a8ed26..4078efb5ad10 100644
--- ui/base/x/x11_window.cc
+++ ui/base/x/x11_window.cc
@@ -190,8 +190,12 @@ void XWindow::Init(const Configuration& config) {
   attribute_mask |= CWBorderPixel;
   swa.border_pixel = 0;
 
+  gfx::AcceleratedWidget parent_widget = config.parent_widget;
+  if (parent_widget == gfx::kNullAcceleratedWidget)
+    parent_widget = x_root_window_;
+
   bounds_in_pixels_ = SanitizeBounds(config.bounds);
-  xwindow_ = XCreateWindow(xdisplay_, x_root_window_, bounds_in_pixels_.x(),
+  xwindow_ = XCreateWindow(xdisplay_, parent_widget, bounds_in_pixels_.x(),
                            bounds_in_pixels_.y(), bounds_in_pixels_.width(),
                            bounds_in_pixels_.height(),
                            0,  // border width
diff --git ui/base/x/x11_window.h ui/base/x/x11_window.h
index 97d8273414fa..b8784d044c61 100644
--- ui/base/x/x11_window.h
+++ ui/base/x/x11_window.h
@@ -20,6 +20,7 @@
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/geometry/size_f.h"
+#include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/x/x11.h"
 #include "ui/gfx/x/x11_types.h"
 
@@ -86,6 +87,7 @@ class COMPONENT_EXPORT(UI_BASE_X) XWindow {
     std::string wm_class_name;
     std::string wm_class_class;
     std::string wm_role_name;
+    gfx::AcceleratedWidget parent_widget;
   };
 
   explicit XWindow(Delegate* delegate);
diff --git ui/views/widget/desktop_aura/desktop_screen_win.cc ui/views/widget/desktop_aura/desktop_screen_win.cc
index 70553b153c44..ecd99bc78373 100644
--- ui/views/widget/desktop_aura/desktop_screen_win.cc
+++ ui/views/widget/desktop_aura/desktop_screen_win.cc
@@ -30,6 +30,8 @@ display::Display DesktopScreenWin::GetDisplayMatching(
 }
 
 HWND DesktopScreenWin::GetHWNDFromNativeView(gfx::NativeView window) const {
+  if (!window)
+    return NULL;
   aura::WindowTreeHost* host = window->GetHost();
   return host ? host->GetAcceleratedWidget() : nullptr;
 }
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
index 7e31a1c159af..eb0451b8913a 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
@@ -95,6 +95,7 @@ DesktopWindowTreeHostWin::DesktopWindowTreeHostWin(
       should_animate_window_close_(false),
       pending_close_(false),
       has_non_client_view_(false),
+      has_external_parent_(false),
       tooltip_(nullptr) {}
 
 DesktopWindowTreeHostWin::~DesktopWindowTreeHostWin() {
@@ -128,8 +129,12 @@ void DesktopWindowTreeHostWin::Init(const Widget::InitParams& params) {
                         native_widget_delegate_);
 
   HWND parent_hwnd = nullptr;
-  if (params.parent && params.parent->GetHost())
+  if (params.parent_widget) {
+    parent_hwnd = params.parent_widget;
+    has_external_parent_ = true;
+  } else if (params.parent && params.parent->GetHost()) {
     parent_hwnd = params.parent->GetHost()->GetAcceleratedWidget();
+  }
 
   remove_standard_frame_ = params.remove_standard_frame;
   has_non_client_view_ = Widget::RequiresNonClientView(params.type);
@@ -891,11 +896,15 @@ void DesktopWindowTreeHostWin::HandleFrameChanged() {
 }
 
 void DesktopWindowTreeHostWin::HandleNativeFocus(HWND last_focused_window) {
-  // TODO(beng): inform the native_widget_delegate_.
+  // See comments in CefBrowserHostImpl::PlatformSetFocus.
+  if (has_external_parent_ && CanActivate())
+    HandleActivationChanged(true);
 }
 
 void DesktopWindowTreeHostWin::HandleNativeBlur(HWND focused_window) {
-  // TODO(beng): inform the native_widget_delegate_.
+  // See comments in CefBrowserHostImpl::PlatformSetFocus.
+  if (has_external_parent_ && CanActivate())
+    HandleActivationChanged(false);
 }
 
 bool DesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_win.h ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
index 335db0db49bb..7f60402ed086 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_win.h
@@ -288,6 +288,10 @@ class VIEWS_EXPORT DesktopWindowTreeHostWin
   // True if the window should have the frame removed.
   bool remove_standard_frame_;
 
+  // True if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent_;
+
   // Owned by TooltipController, but we need to forward events to it so we keep
   // a reference.
   corewm::TooltipWin* tooltip_;
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
index b03a5bc9d509..bcbf960a130e 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_x11.cc
@@ -139,6 +139,7 @@ ui::XWindow::Configuration ConvertInitParamsToX11WindowConfig(
   config.wm_class_name = params.wm_class_name;
   config.wm_class_class = params.wm_class_class;
   config.wm_role_name = params.wm_role_name;
+  config.parent_widget = params.parent_widget;
 
   return config;
 }
@@ -246,6 +247,8 @@ std::vector<aura::Window*> DesktopWindowTreeHostX11::GetAllOpenWindows() {
 }
 
 gfx::Rect DesktopWindowTreeHostX11::GetX11RootWindowBounds() const {
+  if (!screen_bounds_.IsEmpty())
+    return screen_bounds_;
   return x11_window_->bounds();
 }
 
@@ -540,6 +543,8 @@ void DesktopWindowTreeHostX11::GetWindowPlacement(
 }
 
 gfx::Rect DesktopWindowTreeHostX11::GetWindowBoundsInScreen() const {
+  if (!screen_bounds_.IsEmpty())
+    return screen_bounds_;
   gfx::Rect bounds_in_pixels = x11_window_->bounds();
   return ToDIPRect(bounds_in_pixels);
 }
@@ -954,6 +959,9 @@ void DesktopWindowTreeHostX11::SetBoundsInPixels(
 }
 
 gfx::Point DesktopWindowTreeHostX11::GetLocationOnScreenInPixels() const {
+  if (!screen_bounds_.IsEmpty())
+    return screen_bounds_.origin();
+
   return x11_window_->bounds().origin();
 }
 
@@ -1280,6 +1288,11 @@ void DesktopWindowTreeHostX11::InitX11Window(const Widget::InitParams& params) {
   config.background_color = background_color;
   config.prefer_dark_theme = linux_ui && linux_ui->PreferDarkTheme();
   config.icon = ViewsDelegate::GetInstance()->GetDefaultWindowIcon();
+
+  gfx::AcceleratedWidget parent_widget = config.parent_widget;
+  if (parent_widget != gfx::kNullAcceleratedWidget)
+    has_external_parent_ = true;
+
   x11_window_->Init(config);
 
   // Disable compositing on tooltips as a workaround for
diff --git ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
index e32726ad4616..cad33f22bf74 100644
--- ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
+++ ui/views/widget/desktop_aura/desktop_window_tree_host_x11.h
@@ -102,6 +102,12 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   // be changed after.
   void SetVisualId(VisualID visual_id);
 
+  void set_screen_bounds(const gfx::Rect& bounds) { screen_bounds_ = bounds; }
+
+  // Returns true if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent() const { return has_external_parent_; }
+
  protected:
   // Overridden from DesktopWindowTreeHost:
   void Init(const Widget::InitParams& params) override;
@@ -294,6 +300,13 @@ class VIEWS_EXPORT DesktopWindowTreeHostX11
   // behavior if > 0.
   ui::ZOrderLevel z_order_ = ui::ZOrderLevel::kNormal;
 
+  // Override the screen bounds when the host is a child window.
+  gfx::Rect screen_bounds_;
+
+  // True if the widget has a external parent view/window outside of the
+  // Chromium-controlled view/window hierarchy.
+  bool has_external_parent_ = false;
+
   DesktopDragDropClientAuraX11* drag_drop_client_ = nullptr;
 
   std::unique_ptr<ui::EventHandler> x11_non_client_event_filter_;
diff --git ui/views/widget/widget.cc ui/views/widget/widget.cc
index 0cb75272c2ca..ef79679114d4 100644
--- ui/views/widget/widget.cc
+++ ui/views/widget/widget.cc
@@ -157,6 +157,7 @@ Widget::InitParams::InitParams(Type type)
       use_system_default_icon(false),
       show_state(ui::SHOW_STATE_DEFAULT),
       parent(nullptr),
+      parent_widget(gfx::kNullAcceleratedWidget),
       native_widget(nullptr),
       desktop_window_tree_host(nullptr),
       layer_type(ui::LAYER_TEXTURED),
@@ -325,7 +326,7 @@ void Widget::Init(const InitParams& in_params) {
     params.name = params.delegate->GetContentsView()->GetClassName();
 
   params.child |= (params.type == InitParams::TYPE_CONTROL);
-  is_top_level_ = !params.child;
+  is_top_level_ = !params.child || params.parent_widget;
 
   if (params.opacity == views::Widget::InitParams::INFER_OPACITY &&
       params.type != views::Widget::InitParams::TYPE_WINDOW) {
@@ -389,7 +390,12 @@ void Widget::Init(const InitParams& in_params) {
     }
   } else if (params.delegate) {
     SetContentsView(params.delegate->GetContentsView());
-    SetInitialBoundsForFramelessWindow(params.bounds);
+    if (params.parent_widget) {
+      // Set the bounds directly instead of applying an inset.
+      SetBounds(params.bounds);
+    } else {
+      SetInitialBoundsForFramelessWindow(params.bounds);
+    }
   }
   // TODO(https://crbug.com/953978): Use GetNativeTheme() for all platforms.
 #if defined(OS_MACOSX) || defined(OS_WIN)
@@ -1175,10 +1181,16 @@ void Widget::OnNativeWidgetDestroyed() {
 }
 
 gfx::Size Widget::GetMinimumSize() const {
+  gfx::Size size;
+  if (widget_delegate_->MaybeGetMinimumSize(&size))
+    return size;
   return non_client_view_ ? non_client_view_->GetMinimumSize() : gfx::Size();
 }
 
 gfx::Size Widget::GetMaximumSize() const {
+  gfx::Size size;
+  if (widget_delegate_->MaybeGetMaximumSize(&size))
+    return size;
   return non_client_view_ ? non_client_view_->GetMaximumSize() : gfx::Size();
 }
 
diff --git ui/views/widget/widget.h ui/views/widget/widget.h
index 83ba608199b4..546cbe32020c 100644
--- ui/views/widget/widget.h
+++ ui/views/widget/widget.h
@@ -259,6 +259,7 @@ class VIEWS_EXPORT Widget : public internal::NativeWidgetDelegate,
     // Whether the widget should be maximized or minimized.
     ui::WindowShowState show_state;
     gfx::NativeView parent;
+    gfx::AcceleratedWidget parent_widget;
     // Specifies the initial bounds of the Widget. Default is empty, which means
     // the NativeWidget may specify a default size. If the parent is specified,
     // |bounds| is in the parent's coordinate system. If the parent is not
diff --git ui/views/widget/widget_delegate.h ui/views/widget/widget_delegate.h
index 77585733e699..77c5db949902 100644
--- ui/views/widget/widget_delegate.h
+++ ui/views/widget/widget_delegate.h
@@ -191,6 +191,10 @@ class VIEWS_EXPORT WidgetDelegate {
   // be cycled through with keyboard focus.
   virtual void GetAccessiblePanes(std::vector<View*>* panes) {}
 
+  // CEF supports override of min/max size values.
+  virtual bool MaybeGetMinimumSize(gfx::Size* size) const { return false; }
+  virtual bool MaybeGetMaximumSize(gfx::Size* size) const { return false; }
+
  protected:
   virtual ~WidgetDelegate();
 
diff --git ui/views/widget/widget_hwnd_utils.cc ui/views/widget/widget_hwnd_utils.cc
index 9edfa2c00c4b..8a9217578609 100644
--- ui/views/widget/widget_hwnd_utils.cc
+++ ui/views/widget/widget_hwnd_utils.cc
@@ -66,7 +66,7 @@ void CalculateWindowStylesFromInitParams(
       if (!widget_delegate->CanResize())
         *style &= ~(WS_THICKFRAME | WS_MAXIMIZEBOX);
       if (params.remove_standard_frame)
-        *style &= ~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX);
+        *style &= ~(WS_MINIMIZEBOX | WS_MAXIMIZEBOX | WS_CAPTION | WS_SYSMENU);
 
       if (native_widget_delegate->IsDialogBox()) {
         *style |= DS_MODALFRAME;
diff --git ui/views/win/hwnd_message_handler.cc ui/views/win/hwnd_message_handler.cc
index 9b683f301913..8609f61ebd0f 100644
--- ui/views/win/hwnd_message_handler.cc
+++ ui/views/win/hwnd_message_handler.cc
@@ -2963,10 +2963,13 @@ LRESULT HWNDMessageHandler::HandleMouseEventInternal(UINT message,
   } else if (event.type() == ui::ET_MOUSEWHEEL) {
     ui::MouseWheelEvent mouse_wheel_event(msg);
     // Reroute the mouse wheel to the window under the pointer if applicable.
-    return (ui::RerouteMouseWheel(hwnd(), w_param, l_param) ||
-            delegate_->HandleMouseEvent(&mouse_wheel_event))
-               ? 0
-               : 1;
+    if (ui::RerouteMouseWheel(hwnd(), w_param, l_param) ||
+        delegate_->HandleMouseEvent(&mouse_wheel_event)) {
+      SetMsgHandled(TRUE);
+      return 0;
+    } else {
+      return 1;
+    }
   }
 
   // There are cases where the code handling the message destroys the window,