Notify in console when an API fails because it needs to be invoked on user action.

Source/core/page/PointerLockController.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 31 matching lines @@
 {
 }
 
 PassOwnPtrWillBeRawPtr<PointerLockController> PointerLockController::create(Page* page)
 {
     return adoptPtrWillBeNoop(new PointerLockController(page));
 }
 
 void PointerLockController::requestPointerLock(Element* target)
 {
+    if (!UserGestureIndicator::processingUserGesture()) {
+        target->document().executionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel,
+            "requestPointerLock can only be initiated by a user gesture."));

[Mike West, 2014/09/29 12:24:08]

Same here.

[Mayur Kankanwadi, 2014/09/30 13:56:40]

Done.

+    }

[Mike West, 2014/09/29 12:24:08]

You should return early here, right? Otherwise you're not actually blocking the
execution.

[Mayur Kankanwadi, 2014/09/30 13:56:40]

The existing code flow does not do anything noticing the request was not
initiated by user gesture. 
We are just doing a check for posting the console message. There is no intention
to change the existing flow in anyway.

[Mike West, 2014/09/30 14:18:11]

Then I don't understand why you're adding a message. You're saying "Hey, you can
only do this in the context of a user gesture!" but then you let the execution
continue.

Why?

+
     if (!target || !target->inDocument() || m_documentOfRemovedElementWhileWaitingForUnlock) {
         enqueueEvent(EventTypeNames::pointerlockerror, target);
         return;
     }
 
     if (target->document().isSandboxed(SandboxPointerLock)) {
         // FIXME: This message should be moved off the console once a solution to https://bugs.webkit.org/show_bug.cgi?id=103274 exists.
         target->document().addConsoleMessage(ConsoleMessage::create(SecurityMessageSource, ErrorMessageLevel, "Blocked pointer lock on an element because the element's frame is sandboxed and the 'allow-pointer-lock' permission is not set."));
         enqueueEvent(EventTypeNames::pointerlockerror, target);
         return;
@@ skipping 98 matching lines @@
 }
 
 void PointerLockController::trace(Visitor* visitor)
 {
     visitor->trace(m_page);
     visitor->trace(m_element);
     visitor->trace(m_documentOfRemovedElementWhileWaitingForUnlock);
 }
 
 } // namespace blink