User Gesture plumbed from Renderer to Browser's FullscreenController::RequestToLockMouse.

content/public/browser/web_contents_delegate.h

Index: content/public/browser/web_contents_delegate.h
diff --git a/content/public/browser/web_contents_delegate.h b/content/public/browser/web_contents_delegate.h
index 569d1ec62ac790da5c589c24599f4a63a65f2e5d..ecfdb7a7498bece55e73dc80d3a3c972bc3f73fd 100644
--- a/content/public/browser/web_contents_delegate.h
+++ b/content/public/browser/web_contents_delegate.h
@@ -391,7 +391,8 @@ class CONTENT_EXPORT WebContentsDelegate {
   // Requests to lock the mouse. Once the request is approved or rejected,
   // GotResponseToLockMouseRequest() will be called on the requesting tab
   // contents.
-  virtual void RequestToLockMouse(WebContents* web_contents) {}
+  virtual void RequestToLockMouse(WebContents* web_contents,
+                                  bool user_gesture) {}
 
   // Notification that the page has lost the mouse lock.
   virtual void LostMouseLock() {}