Disallow users modify canvas after it transfers control to offscreen

third_party/WebKit/Source/modules/canvas2d/CanvasRenderingContext2DTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/canvas2d/CanvasRenderingContext2D.h"
 
 #include "core/dom/Document.h"
 #include "core/fetch/MemoryCache.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/ImageBitmap.h"
@@ skipping 661 matching lines @@
 
     context2d()->fillText("Text", 0, 5);
 }
 
 TEST_F(CanvasRenderingContext2DTest, ImageResourceLifetime)
 {
     NonThrowableExceptionState nonThrowableExceptionState;
     Element* canvasElement = document().createElement("canvas", nonThrowableExceptionState);
     EXPECT_FALSE(nonThrowableExceptionState.hadException());
     HTMLCanvasElement* canvas = static_cast<HTMLCanvasElement*>(canvasElement);
-    canvas->setHeight(40);
-    canvas->setWidth(40);
+    canvas->setSize(IntSize(40, 40));
     ImageBitmap* imageBitmapDerived = nullptr;
     {
         const ImageBitmapOptions defaultOptions;
         Optional<IntRect> cropRect = IntRect(0, 0, canvas->width(), canvas->height());
         ImageBitmap* imageBitmapFromCanvas = ImageBitmap::create(canvas, cropRect, defaultOptions);
         cropRect = IntRect(0, 0, 20, 20);
         imageBitmapDerived = ImageBitmap::create(imageBitmapFromCanvas, cropRect, defaultOptions);
     }
     CanvasContextCreationAttributes attributes;
     CanvasRenderingContext2D* context = static_cast<CanvasRenderingContext2D*>(canvas->getCanvasRenderingContext("2d", attributes));
@@ skipping 159 matching lines @@
     EXPECT_FALSE(canvasElement().buffer()->isAccelerated());
 
     context->fillRect(10, 10, 100, 100);
 
     EXPECT_EQ(0, getCurrentGPUMemoryUsage());
     EXPECT_EQ(0, getGlobalGPUMemoryUsage());
     EXPECT_EQ(0u, getGlobalAcceleratedImageBufferCount());
 }
 
 } // namespace blink