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/native/browser_platform_delegate_native.h

@@ -32,6 +32,7 @@ class CefBrowserPlatformDelegateNative
   // CefBrowserPlatformDelegate methods:
   SkColor GetBackgroundColor() const override;
   void WasResized() override;
+  void NotifyScreenInfoChanged() override;
 
   // Translate CEF events to Chromium/Blink Web events.
   virtual input::NativeWebKeyboardEvent TranslateWebKeyEvent(