Make UnacceleratedBufferSurface use a SkSurface instead of a SkCanvas

Source/platform/graphics/UnacceleratedImageBufferSurface.cpp

 /*
  * Copyright (c) 2013, Google Inc. 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "platform/graphics/UnacceleratedImageBufferSurface.h"
 
-#include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkSurface.h"
 #include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
 UnacceleratedImageBufferSurface::UnacceleratedImageBufferSurface(const IntSize& size, OpacityMode opacityMode)
     : ImageBufferSurface(size, opacityMode)
-    , m_canvas(adoptRef(SkCanvas::NewRasterN32(size.width(), size.height())))
+    , m_surface(adoptRef(SkSurface::NewRasterPMColor(size.width(), size.height())))
 {
-    if (m_canvas)
+    if (m_surface)
         clear();
 }
 
+UnacceleratedImageBufferSurface::~UnacceleratedImageBufferSurface() { }
+
+SkCanvas* UnacceleratedImageBufferSurface::canvas() const
+{
+    return m_surface->getCanvas();
+}
+
+bool UnacceleratedImageBufferSurface::isValid() const
+{
+    return m_surface;
+}
+
 } // namespace WebCore