Check If ImageBuffer is allocated before proceeding.

Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp

Index: Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp
diff --git a/Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp b/Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp
index 66a10d6f9574c2d0cbb2e50b283e564ee6a5f524..f243a6ffb583d963c34c29e7a02084247b171e46 100644
--- a/Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp
+++ b/Source/platform/graphics/RecordingImageBufferSurfaceTest.cpp
@@ -84,6 +84,7 @@ protected:
         // We create an ImageBuffer in order for the testSurface to be
         // properly initialized with a GraphicsContext
         m_imageBuffer = ImageBuffer::create(testSurface.release());
+        EXPECT_FALSE(!m_imageBuffer);
         m_fakeImageBufferClient = adoptPtr(new FakeImageBufferClient(m_imageBuffer.get()));
         m_imageBuffer->setClient(m_fakeImageBufferClient.get());
     }