Ensured that any failure to create a WebGL context dispatches a webglcontextcreationerror

Source/core/html/canvas/WebGLRenderingContext.cpp

Index: Source/core/html/canvas/WebGLRenderingContext.cpp
diff --git a/Source/core/html/canvas/WebGLRenderingContext.cpp b/Source/core/html/canvas/WebGLRenderingContext.cpp
index 190ad7665c36387dcef80c6a83105d05ed2cca59..b0f5542b7474a719a86b938f0546fda843465889 100644
--- a/Source/core/html/canvas/WebGLRenderingContext.cpp
+++ b/Source/core/html/canvas/WebGLRenderingContext.cpp
@@ -62,8 +62,10 @@ PassOwnPtr<WebGLRenderingContext> WebGLRenderingContext::create(HTMLCanvasElemen
 {
     Document& document = canvas->document();
     LocalFrame* frame = document.frame();
-    if (!frame)
+    if (!frame) {
+        canvas->dispatchEvent(WebGLContextEvent::create(EventTypeNames::webglcontextcreationerror, false, true, "Web page was not allowed to create a WebGL context."));
         return nullptr;
+    }
     Settings* settings = frame->settings();
 
     // The FrameLoaderClient might block creation of a new WebGL context despite the page settings; in