Label info for webglcontext should have pointer data.

Source/core/html/canvas/WebGLRenderingContext.cpp

 /*
  * Copyright (C) 2009 Apple 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 102 matching lines @@
             }
             statusMessage.append(".");
         }
         canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, statusMessage));
         return nullptr;
     }
 
     OwnPtr<Extensions3DUtil> extensionsUtil = Extensions3DUtil::create(context.get());
     if (!extensionsUtil)
         return nullptr;
-    if (extensionsUtil->supportsExtension("GL_EXT_debug_marker"))
-        context->pushGroupMarkerEXT("WebGLRenderingContext");
+    if (extensionsUtil->supportsExtension("GL_EXT_debug_marker")) {
+        String contextLabel("WebGLRenderingContext-");
+        contextLabel.append(String::format("%p", context.get()));
+        context->pushGroupMarkerEXT(contextLabel.utf8().data());

[vmiura, 2015/01/30 22:08:48]

The API expects ASCII encoding, so could you please use ASCII string to be
specific.

Thanks!

[sivag, 2015/02/02 06:34:36]

Done.

+    }
 
     OwnPtrWillBeRawPtr<WebGLRenderingContext> renderingContext = adoptPtrWillBeNoop(new WebGLRenderingContext(canvas, context.release(), attributes));
     renderingContext->registerContextExtensions();
     renderingContext->suspendIfNeeded();
 
     if (!renderingContext->drawingBuffer()) {
         canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "Could not create a WebGL context."));
         return nullptr;
     }
 
@@ skipping 66 matching lines @@
     visitor->trace(m_webglDepthTexture);
     WebGLRenderingContextBase::trace(visitor);
 }
 
 void WebGLRenderingContext::forceNextWebGLContextCreationToFail()
 {
     shouldFailContextCreationForTesting = true;
 }
 
 } // namespace blink