Re-land "WebGL: Transfer ownership of WebGraphicsContext3D to DrawingBuffer"

Source/platform/graphics/gpu/DrawingBufferTest.cpp

Index: Source/platform/graphics/gpu/DrawingBufferTest.cpp
diff --git a/Source/platform/graphics/gpu/DrawingBufferTest.cpp b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
index 2a9fb38d59431abc8b1d6844eb98f7a2c06c23d0..1ffc89bf61a4c2622e18a3238f1ec0034b29e7b4 100644
--- a/Source/platform/graphics/gpu/DrawingBufferTest.cpp
+++ b/Source/platform/graphics/gpu/DrawingBufferTest.cpp
@@ -110,16 +110,17 @@ protected:
     virtual void SetUp()
     {
         RefPtr<FakeContextEvictionManager> contextEvictionManager = adoptRef(new FakeContextEvictionManager());
-        m_context = adoptPtr(new WebGraphicsContext3DForTests);
-        m_drawingBuffer = DrawingBuffer::create(m_context.get(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
+        OwnPtr<WebGraphicsContext3DForTests> context = adoptPtr(new WebGraphicsContext3DForTests);
+        m_context = context.get();
+        m_drawingBuffer = DrawingBuffer::create(context.release(), IntSize(initialWidth, initialHeight), DrawingBuffer::Preserve, contextEvictionManager.release());
     }
 
     WebGraphicsContext3DForTests* webContext()
     {
-        return m_context.get();
+        return m_context;
     }
 
-    OwnPtr<WebGraphicsContext3DForTests> m_context;
+    WebGraphicsContext3DForTests* m_context;
     RefPtr<DrawingBuffer> m_drawingBuffer;
 };
 
@@ -137,16 +138,6 @@ TEST_F(DrawingBufferTest, testPaintRenderingResultsToCanvas)
     EXPECT_FALSE(imageBuffer->bitmap().isNull());
 }
 
-TEST_F(DrawingBufferTest, verifyNoNewBuffersAfterContextLostWithMailboxes)
-{
-    // Tell the buffer its contents changed and context was lost.
-    m_drawingBuffer->markContentsChanged();
-    m_drawingBuffer->releaseResources();
-
-    blink::WebExternalTextureMailbox mailbox;
-    EXPECT_FALSE(m_drawingBuffer->prepareMailbox(&mailbox, 0));
-}
-
 TEST_F(DrawingBufferTest, verifyResizingProperlyAffectsMailboxes)
 {
     blink::WebExternalTextureMailbox mailbox;