Implement pointer lock API for out-of-process iframes.

content/browser/frame_host/cross_process_frame_connector.h

Index: content/browser/frame_host/cross_process_frame_connector.h
diff --git a/content/browser/frame_host/cross_process_frame_connector.h b/content/browser/frame_host/cross_process_frame_connector.h
index a1e04d8ae2456046f827694a27d386439eafcd01..9ecf45b1df04a9bc9eabd7a9bcd802f6d8d94746 100644
--- a/content/browser/frame_host/cross_process_frame_connector.h
+++ b/content/browser/frame_host/cross_process_frame_connector.h
@@ -107,6 +107,9 @@ class CONTENT_EXPORT CrossProcessFrameConnector {
   // Focuses the root RenderWidgetHostView.
   void FocusRootView();
 
+  // Locks the mouse. Returns true if mouse is locked.
+  bool LockMouse();
+
   // Returns the parent RenderWidgetHostView or nullptr it it doesn't have one.
   virtual RenderWidgetHostViewBase* GetParentRenderWidgetHostView();