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.

libcef/browser/browser_contents_delegate.h

@@ -87,6 +87,10 @@ class CefBrowserContentsDelegate : public content::WebContentsDelegate,
       base::OnceCallback<void(content::NavigationHandle&)>&
           navigation_handle_callback);
 
+  // Same as SetContentsBounds but returning false if unhandled.
+  bool SetContentsBoundsEx(content::WebContents* source,
+                           const gfx::Rect& bounds);
+
   // WebContentsDelegate methods:
   void LoadingStateChanged(content::WebContents* source,
                            bool should_show_loading_ui) override;