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

Source/core/dom/Fullscreen.cpp

Index: Source/core/dom/Fullscreen.cpp
diff --git a/Source/core/dom/Fullscreen.cpp b/Source/core/dom/Fullscreen.cpp
index 64b67a512ecf0eaffa02f3a1ab79bd769c43df31..20f48fba4347a122ab4667150967c751ab4855b0 100644
--- a/Source/core/dom/Fullscreen.cpp
+++ b/Source/core/dom/Fullscreen.cpp
@@ -231,8 +231,11 @@ void Fullscreen::requestFullscreen(Element& element, RequestType requestType)
         //   An algorithm is allowed to show a pop-up if, in the task in which the algorithm is running, either:
         //   - an activation behavior is currently being processed whose click event was trusted, or
         //   - the event listener for a trusted click event is being handled.
-        if (!UserGestureIndicator::processingUserGesture())
+        if (!UserGestureIndicator::processingUserGesture()) {
+            document()->executionContext()->addConsoleMessage(ConsoleMessage::create(JSMessageSource, WarningMessageLevel,
+                "requestFullScreen() can only be intiated by a user gesture."));

[felt, 2014/09/25 08:48:39]

Should we save this string "can only be initiated by a user gesture" somewhere
for reuse with the same string, if/when it needs to be added for other APIs?
That way we don't end up with different strings in different places.

[Mayur Kankanwadi, 2014/09/25 08:59:07]

Though I haven't noticed this usage pattern before anywhere in Blink/Webkit, we
can probably give it a shot.
Just a simple search for throwDOMException shows the amount of string
duplication within Blink. 
We can target this as a separate bug, where in we replace duplicated exception
or console log strings with AtomicStrings.
Does it sound good?

[felt, 2014/09/26 05:35:46]

Fine with me.

[meacer, 2014/09/26 17:47:38]

intiated -> initiated

I don't think you need parenthesis either.
"requestFullScreen can only be initiated by a user gesture" looks clearer.

[Mayur Kankanwadi, 2014/09/29 11:22:13]

Done.

             break;
+        }
 
         // Fullscreen is not supported.
         if (!fullscreenIsSupported(element.document(), element))