Fix browser focus assignment on mouse click (fixes issue #3306)

DesktopWindowTreeHostWin ("Chrome_WidgetWin_0") focus needs to be set before
the associated call to WebContents::Focus. In the case of mouse click events,
this means ::SetFocus needs to be called explicitly. See updated comments in
CefBrowserPlatformDelegateNativeWin::SetFocus.

libcef/browser/native/browser_platform_delegate_native_win.cc

@@ -354,17 +354,26 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
     // Give native focus to the DesktopWindowTreeHostWin ("Chrome_WidgetWin_0")
     // associated with the root window. The currently focused HWND may be
     // "CefBrowserWindow" if we're called in response to our WndProc receiving
-    // the WM_SETFOCUS event, or some other HWND if the client calls
+    // the WM_SETFOCUS event (possibly due to "CefBrowserWindow" recieving the
-    // CefBrowserHost::SetFocus(true) directly.
+    // top-level WM_ACTIVATE event), or some other HWND if the client calls
+    // CefBrowserHost::SetFocus(true) directly. DesktopWindowTreeHostWin may
+    // also receive focus/blur and mouse click events from the OS directly, in
+    // which case this method will not be called but the below discussion still
+    // applies.
     //
-    // The DesktopWindowTreeHostWin HandleNativeFocus/HandleNativeBlur methods
+    // The DesktopWindowTreeHostWin::HandleNativeFocus/HandleNativeBlur methods
     // are called in response to WM_SETFOCUS/WM_KILLFOCUS respectively. The
-    // implementation has been patched to call HandleActivationChanged which
+    // DesktopWindowTreeHostWin::HandleMouseEvent method is called if the user
-    // results in the following behaviors:
+    // clicks on the WebContents. These methods have all been patched to call
+    // HandleActivationChanged (indirectly via ::SetFocus in the case of mouse
+    // clicks). HandleActivationChanged will then trigger the following
+    // behaviors:
     // 1. Update focus/activation state of the aura::Window indirectly via
     //    wm::FocusController. This allows focus-related behaviors (e.g. focus
     //    rings, flashing caret, onFocus/onBlur JS events, etc.) to work as
-    //    expected (see issue #1677).
+    //    expected (see issue #1677) and also triggers an initial call to
+    //    WebContents::Focus which gives logical focus to the
+    //    RenderWidgetHostViewAura in the views hierarchy (see issue #3306).
     // 2. Update focus state of the ui::InputMethod. If this does not occur
     //    then:
     //    (a) InputMethodBase::GetTextInputClient will return NULL and
@@ -376,7 +385,8 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
     //    causing TSF not to handle IME events (see issue #3306). For this same
     //    reason, ::SetFocus needs to be called before WebContents::Focus which
     //    sends the InputMethod OnWillChangeFocusedClient notification that then
-    //    calls IsWindowFocused.
+    //    calls IsWindowFocused (e.g. WebContents::Focus is intentionally called
+    //    multiple times).
     //
     // This differs from activation in Chrome which is handled via
     // HWNDMessageHandler::PostProcessActivateMessage (Widget::Show indirectly
@@ -395,8 +405,10 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
 
   if (web_contents_) {
     // Give logical focus to the RenderWidgetHostViewAura in the views
-    // hierarchy. This does not change the native keyboard focus. See above
+    // hierarchy. This does not change the native keyboard focus. When
-    // comments about InputMethod notifications.
+    // |window_widget_| exists this additional Focus() call is necessary to
+    // correctly assign focus/input state after native focus resulting from
+    // window activation (see the InputMethod discussion above).
     web_contents_->Focus();
   }
 }

patch/patches/views_widget.patch

@@ -258,7 +258,7 @@ index ff670d8099968..f39fd6972e304 100644
  
    // Calculate initial bounds.
 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 d7260950ca1ba..67664a29e3510 100644
+index d7260950ca1ba..f18a52e61446c 100644
 --- ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
 +++ ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
 @@ -181,8 +181,12 @@ void DesktopWindowTreeHostWin::Init(const Widget::InitParams& params) {
@@ -280,19 +280,32 @@ index d7260950ca1ba..67664a29e3510 100644
  
  void DesktopWindowTreeHostWin::HandleNativeFocus(HWND last_focused_window) {
 -  // TODO(beng): inform the native_widget_delegate_.
-+  // See comments in CefBrowserHostImpl::PlatformSetFocus.
++  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
 +  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.
++  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
 +  if (has_external_parent_ && CanActivate())
 +    HandleActivationChanged(false);
  }
  
  bool DesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
+@@ -1001,6 +1009,12 @@ bool DesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
+   if (ui::PlatformEventSource::ShouldIgnoreNativePlatformEvents())
+     return true;
+ 
++  // See comments in CefBrowserPlatformDelegateNativeWin::SetFocus.
++  if (has_external_parent_ && CanActivate() && event->IsAnyButton() &&
++      ::GetFocus() != GetHWND()) {
++    ::SetFocus(GetHWND());
++  }
++
+   SendEventToSink(event);
+   return event->handled();
+ }
 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 0aae49ec83b88..ab61925742ed7 100644
 --- ui/views/widget/desktop_aura/desktop_window_tree_host_win.h