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

Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp

Index: Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp
diff --git a/Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp b/Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp
index ae2010e3aeb3b76635d2e0bd02c4e8d8f775c8dd..60d9a8a1681fb2ed7b0c65848d34d934bc9f7de4 100644
--- a/Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp
+++ b/Source/bindings/v8/custom/V8HTMLCanvasElementCustom.cpp
@@ -60,25 +60,25 @@ void V8HTMLCanvasElement::getContextMethodCustom(const v8::FunctionCallbackInfo<
         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;
@@ -87,7 +87,7 @@ void V8HTMLCanvasElement::getContextMethodCustom(const v8::FunctionCallbackInfo<
         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;