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 214858aa156975ac3427fd753047493e60a4902a..d72969de132c48933df9f613545ab7aae46921a0 100644
--- a/content/browser/frame_host/cross_process_frame_connector.h
+++ b/content/browser/frame_host/cross_process_frame_connector.h
@@ -110,6 +110,9 @@ 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();