Support JavaScript window.moveTo/By() and resizeTo/By() (fixes #698)

Adds new CefDisplayHandler::OnContentsBoundsChange and
CefDisplayHandler::GetRootWindowScreenRect callbacks.

cefclient: Implement the above callbacks and call
CefBrowserHost::NotifyScreenInfoChanged when the root window
bounds change.

cefclient: osr: Use real screen bounds by default. Pass
`--fake-screen-bounds` for the old default behavior.

Load https://tests/window in cefclient for additional
implementation details and usage examples.

include/cef_browser.h

@@ -707,12 +707,24 @@ class CefBrowserHost : public virtual CefBaseRefCounted {
   virtual void WasHidden(bool hidden) = 0;
 
   ///
-  /// Send a notification to the browser that the screen info has changed. The
-  /// browser will then call CefRenderHandler::GetScreenInfo to update the
-  /// screen information with the new values. This simulates moving the webview
-  /// window from one display to another, or changing the properties of the
-  /// current display. This method is only used when window rendering is
-  /// disabled.
+  /// Notify the browser that screen information has changed. Updated
+  /// information will be sent to the renderer process to configure screen size
+  /// and position values used by CSS and JavaScript (window.deviceScaleFactor,
+  /// window.screenX/Y, window.outerWidth/Height, etc.). For background see
+  /// https://bitbucket.org/chromiumembedded/cef/wiki/GeneralUsage.md#markdown-header-coordinate-systems
+  ///
+  /// This method is used with (a) windowless rendering and (b) windowed
+  /// rendering with external (client-provided) root window.
+  ///
+  /// With windowless rendering the browser will call
+  /// CefRenderHandler::GetScreenInfo, CefRenderHandler::GetRootScreenRect and
+  /// CefRenderHandler::GetViewRect. This simulates moving or resizing the root
+  /// window in the current display, moving the root window from one display to
+  /// another, or changing the properties of the current display.
+  ///
+  /// With windowed rendering the browser will call
+  /// CefDisplayHandler::GetRootWindowScreenRect and use the associated
+  /// display properties.
   ///
   /*--cef()--*/
   virtual void NotifyScreenInfoChanged() = 0;

include/cef_display_handler.h

@@ -38,6 +38,7 @@
 #define CEF_INCLUDE_CEF_DISPLAY_HANDLER_H_
 #pragma once
 
+#include "include/cef_api_hash.h"
 #include "include/cef_base.h"
 #include "include/cef_browser.h"
 #include "include/cef_frame.h"
@@ -123,7 +124,7 @@ class CefDisplayHandler : public virtual CefBaseRefCounted {
   ///
   /// Called when auto-resize is enabled via
   /// CefBrowserHost::SetAutoResizeEnabled and the contents have auto-resized.
-  /// |new_size| will be the desired size in view coordinates. Return true if
+  /// |new_size| will be the desired size in DIP coordinates. Return true if
   /// the resize was handled or false for default handling.
   ///
   /*--cef()--*/
@@ -162,6 +163,46 @@ class CefDisplayHandler : public virtual CefBaseRefCounted {
   virtual void OnMediaAccessChange(CefRefPtr<CefBrowser> browser,
                                    bool has_video_access,
                                    bool has_audio_access) {}
+
+#if CEF_API_ADDED(CEF_NEXT)
+  ///
+  /// Called when JavaScript is requesting new bounds via window.moveTo/By() or
+  /// window.resizeTo/By(). |new_bounds| are in DIP screen coordinates.
+  ///
+  /// With Views-hosted browsers |new_bounds| are the desired bounds for
+  /// the containing CefWindow and may be passed directly to
+  /// CefWindow::SetBounds. With external (client-provided) parent on macOS and
+  /// Windows |new_bounds| are the desired frame bounds for the containing root
+  /// window. With other non-Views browsers |new_bounds| are the desired bounds
+  /// for the browser content only unless the client implements either
+  /// CefDisplayHandler::GetRootWindowScreenRect for windowed browsers or
+  /// CefRenderHandler::GetWindowScreenRect for windowless browsers. Clients may
+  /// expand browser content bounds to window bounds using OS-specific or
+  /// CefDisplay methods.
+  ///
+  /// Return true if this method was handled or false for default handling.
+  /// Default move/resize behavior is only provided with Views-hosted Chrome
+  /// style browsers.
+  ///
+  /*--cef(added=next)--*/
+  virtual bool OnContentsBoundsChange(CefRefPtr<CefBrowser> browser,
+                                      const CefRect& new_bounds) {
+    return false;
+  }
+
+  ///
+  /// Called to retrieve the external (client-provided) root window rectangle in
+  /// screen DIP coordinates. Only called for windowed browsers on Windows and
+  /// Linux. Return true if the rectangle was provided. Return false to use the
+  /// root window bounds on Windows or the browser content bounds on Linux. For
+  /// additional usage details see CefBrowserHost::NotifyScreenInfoChanged.
+  ///
+  /*--cef(added=next)--*/
+  virtual bool GetRootWindowScreenRect(CefRefPtr<CefBrowser> browser,
+                                       CefRect& rect) {
+    return false;
+  }
+#endif
 };
 
 #endif  // CEF_INCLUDE_CEF_DISPLAY_HANDLER_H_

include/views/cef_display.h

@@ -50,6 +50,9 @@
 /// indicated. Methods must be called on the browser process UI thread unless
 /// otherwise indicated.
 ///
+/// For details on coordinate systems and usage see
+/// https://bitbucket.org/chromiumembedded/cef/wiki/GeneralUsage#markdown-header-coordinate-systems
+///
 /*--cef(source=library)--*/
 class CefDisplay : public CefBaseRefCounted {
  public:
@@ -129,7 +132,9 @@ class CefDisplay : public CefBaseRefCounted {
   /// Returns this Display's device pixel scale factor. This specifies how much
   /// the UI should be scaled when the actual output has more pixels than
   /// standard displays (which is around 100~120dpi). The potential return
-  /// values differ by platform.
+  /// values differ by platform. Windowed browsers with 1.0 zoom will have a
+  /// JavaScript `window.devicePixelRatio` value matching the associated
+  /// Display's GetDeviceScaleFactor() value.
   ///
   /*--cef()--*/
   virtual float GetDeviceScaleFactor() = 0;