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_host_base.h

@@ -265,6 +265,7 @@ class CefBrowserHostBase : public CefBrowserHost,
   void SetAudioMuted(bool mute) override;
   bool IsAudioMuted() override;
   void NotifyMoveOrResizeStarted() override;
+  void NotifyScreenInfoChanged() override;
   bool IsFullscreen() override;
   void ExitFullscreen(bool will_cause_resize) override;
   bool IsRenderProcessUnresponsive() override;