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

Source/core/html/HTMLCanvasElement.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. 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.
@@ skipping 135 matching lines @@
 }
 
 CanvasRenderingContext* HTMLCanvasElement::getContext(const String& type, CanvasContextAttributes* attrs)
 {
     // A Canvas can either be "2D" or "webgl" but never both. If you request a 2D canvas and the existing
     // context is already 2D, just return that. If the existing context is WebGL, then destroy it
     // before creating a new 2D context. Vice versa when requesting a WebGL canvas. Requesting a
     // context with any other type string will destroy any existing context.
     enum ContextType {
         Context2d,
-        ContextWebkit3d,
-        ContextExperimentalWebgl,
+        // Retain the enum values 'as is' as these are used by the histograms.
+        ContextExperimentalWebgl = 2,

[rune, 2014/08/22 12:15:50]

I think it would be safer to explicitly assign a value to each enum. See how
it's done for the Feature enum in the UseCounter class.

[rune, 2014/08/22 12:15:50]

I think it would be safer to explicitly assign a value to each enum. See how
it's done for the Feature enum in the UseCounter class.

         ContextWebgl,
         // Only add new items to the end and keep the order of existing items.

[rune, 2014/08/22 12:15:50]

The comment in UseCounter for Feature looks clearer:

// Do not change assigned numbers of existing items: add new features
// to the end of the list.

Please consider using that comment and move it to the top of the enum.

         ContextTypeCount,
     };
 
     // FIXME - The code depends on the context not going away once created, to prevent JS from
     // seeing a dangling pointer. So for now we will disallow the context from being changed
     // once it is created.
     if (type == "2d") {
         if (m_context && !m_context->is2d())
             return 0;
         if (!m_context) {
@@ skipping 570 matching lines @@
 {
     return !originClean();
 }
 
 FloatSize HTMLCanvasElement::sourceSize() const
 {
     return FloatSize(width(), height());
 }
 
 }