Add initial Blink-side support for the Screen Orientation API

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 7568ee13b4d53034e2b82033af8d63ed53f00586..bcb902269c65858283cdf870b57fe3f286fdca86 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -88,6 +88,7 @@ class LinkHighlight;
 class MIDIClientProxy;
 class PinchViewports;
 class PrerendererClientImpl;
+class ScreenOrientationClientProxy;
 class SpeechInputClientImpl;
 class SpeechRecognitionClientProxy;
 class UserMediaClientImpl;
@@ -757,6 +758,7 @@ private:
     OwnPtr<SpeechRecognitionClientProxy> m_speechRecognitionClient;
 
     OwnPtr<GeolocationClientProxy> m_geolocationClientProxy;
+    OwnPtr<ScreenOrientationClientProxy> m_screenOrientationClientProxy;
 
     UserMediaClientImpl m_userMediaClientImpl;
     OwnPtr<MIDIClientProxy> m_midiClientProxy;