canvas.getContext with alpha:undefined should behave like alpha:true

Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp

 /*
  * Copyright (C) 2007-2009 Google Inc. All rights reserved.
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 42 matching lines @@
     v8::Isolate* isolate = info.GetIsolate();
     HTMLCanvasElement* impl = V8HTMLCanvasElement::toNative(holder);
     TOSTRING_VOID(V8StringResource<>, contextIdResource, info[0]);
     String contextId = contextIdResource;
     RefPtr<CanvasContextAttributes> attributes;
     if (contextId == "webgl" || contextId == "experimental-webgl") {
         RefPtr<WebGLContextAttributes> webGLAttributes = WebGLContextAttributes::create();
         if (info.Length() > 1 && info[1]->IsObject()) {
             v8::Handle<v8::Object> jsAttributes = info[1]->ToObject();
             v8::Handle<v8::String> alpha = v8AtomicString(isolate, "alpha");
-            if (jsAttributes->Has(alpha))
+            if (jsAttributes->Has(alpha) && !isUndefinedOrNull(jsAttributes->Get(alpha)))
                 webGLAttributes->setAlpha(jsAttributes->Get(alpha)->BooleanValue());
             v8::Handle<v8::String> depth = v8AtomicString(isolate, "depth");
-            if (jsAttributes->Has(depth))
+            if (jsAttributes->Has(depth) && !isUndefinedOrNull(jsAttributes->Get(depth)))
                 webGLAttributes->setDepth(jsAttributes->Get(depth)->BooleanValue());
             v8::Handle<v8::String> stencil = v8AtomicString(isolate, "stencil");
-            if (jsAttributes->Has(stencil))
+            if (jsAttributes->Has(stencil) && !isUndefinedOrNull(jsAttributes->Get(stencil)))
                 webGLAttributes->setStencil(jsAttributes->Get(stencil)->BooleanValue());
             v8::Handle<v8::String> antialias = v8AtomicString(isolate, "antialias");
-            if (jsAttributes->Has(antialias))
+            if (jsAttributes->Has(antialias) && !isUndefinedOrNull(jsAttributes->Get(antialias)))
                 webGLAttributes->setAntialias(jsAttributes->Get(antialias)->BooleanValue());
             v8::Handle<v8::String> premultipliedAlpha = v8AtomicString(isolate, "premultipliedAlpha");
-            if (jsAttributes->Has(premultipliedAlpha))
+            if (jsAttributes->Has(premultipliedAlpha) && !isUndefinedOrNull(jsAttributes->Get(premultipliedAlpha)))
                 webGLAttributes->setPremultipliedAlpha(jsAttributes->Get(premultipliedAlpha)->BooleanValue());
             v8::Handle<v8::String> preserveDrawingBuffer = v8AtomicString(isolate, "preserveDrawingBuffer");
-            if (jsAttributes->Has(preserveDrawingBuffer))
+            if (jsAttributes->Has(preserveDrawingBuffer) && !isUndefinedOrNull(jsAttributes->Get(preserveDrawingBuffer)))
                 webGLAttributes->setPreserveDrawingBuffer(jsAttributes->Get(preserveDrawingBuffer)->BooleanValue());
             v8::Handle<v8::String> failIfMajorPerformanceCaveat = v8AtomicString(isolate, "failIfMajorPerformanceCaveat");
-            if (jsAttributes->Has(failIfMajorPerformanceCaveat))
+            if (jsAttributes->Has(failIfMajorPerformanceCaveat) && !isUndefinedOrNull(jsAttributes->Get(failIfMajorPerformanceCaveat)))
                 webGLAttributes->setFailIfMajorPerformanceCaveat(jsAttributes->Get(failIfMajorPerformanceCaveat)->BooleanValue());
         }
         attributes = webGLAttributes;
     } else {
         RefPtr<Canvas2DContextAttributes> canvas2DAttributes = Canvas2DContextAttributes::create();
         if (info.Length() > 1 && info[1]->IsObject()) {
             v8::Handle<v8::Object> jsAttributes = info[1]->ToObject();
             v8::Handle<v8::String> alpha = v8AtomicString(isolate, "alpha");
-            if (jsAttributes->Has(alpha))
+            if (jsAttributes->Has(alpha) && !isUndefinedOrNull(jsAttributes->Get(alpha)))
                 canvas2DAttributes->setAlpha(jsAttributes->Get(alpha)->BooleanValue());
         }
         attributes = canvas2DAttributes;
     }
     CanvasRenderingContext* result = impl->getContext(contextId, attributes.get());
     if (!result) {
         v8SetReturnValueNull(info);
         return;
     }
     if (result->is2d()) {
@@ skipping 41 matching lines @@
         quality = info[1]->NumberValue();
         qualityPtr = &quality;
     }
 
     String result = canvas->toDataURL(type, qualityPtr, exceptionState);
     exceptionState.throwIfNeeded();
     v8SetReturnValueStringOrUndefined(info, result, info.GetIsolate());
 }
 
 } // namespace WebCore