Remove unused enum declaration ContextWebkit3d from HTMLCanvasElement::getContext()

Source/core/html/HTMLCanvasElement.cpp

Index: Source/core/html/HTMLCanvasElement.cpp
diff --git a/Source/core/html/HTMLCanvasElement.cpp b/Source/core/html/HTMLCanvasElement.cpp
index e84eacf3bb509305325d62e996b246c48cc15f87..bdc977d6671de40d198adccfc3f966bc3034318e 100644
--- a/Source/core/html/HTMLCanvasElement.cpp
+++ b/Source/core/html/HTMLCanvasElement.cpp
@@ -153,7 +153,6 @@ CanvasRenderingContext* HTMLCanvasElement::getContext(const String& type, Canvas
     // context with any other type string will destroy any existing context.
     enum ContextType {
         Context2d,
-        ContextWebkit3d,
         ContextExperimentalWebgl,
         ContextWebgl,
         // Only add new items to the end and keep the order of existing items.

[rune, 2014/08/19 08:47:49]

This is not my area of expertise, so you should try to find someone who has.
However, the comment above indicates that the integer values for the enums above
is important, so removing one of the enums might break something.

[rune, 2014/08/19 08:52:03]

Looking further down the code, the integer value of the enum is used for
histograms, so not lgtm.

[vivekg, 2014/08/19 10:58:07]

Thank you for the review @rune.

Agreed that the total number of enums i.e. ContextTypeCount value is used for
the histograms. I am not sure though whether this would break anything
specifically. Also all the other enums values are used for comparisons but
ContextWebkit3d. Not sure its worth keeping it here. 

I am also adding @junov for the feedback.