Support currentTransform in 2D Canvas.

Source/core/html/canvas/CanvasRenderingContext2D.h

Index: Source/core/html/canvas/CanvasRenderingContext2D.h
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.h b/Source/core/html/canvas/CanvasRenderingContext2D.h
index a3f8eb1cfa2181615fba78ba660f01fa79ebf0d4..72e2459c2d25f6acbc32a257c55076b62ed0b331 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.h
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.h
@@ -36,6 +36,8 @@
 #include "core/platform/graphics/ImageBuffer.h"
 #include "core/platform/graphics/Path.h"
 #include "core/platform/graphics/transforms/AffineTransform.h"
+#include "core/svg/SVGMatrix.h"
+#include "core/svg/properties/SVGPropertyTearOff.h"
 #include "wtf/HashMap.h"
 #include "wtf/Vector.h"
 #include "wtf/text/WTFString.h"
@@ -117,6 +119,20 @@ public:
     void save() { ++m_unrealizedSaveCount; }
     void restore();
 
+    // TODO(dshwang): Need to clean up currentTransform binding methods via improving binding generator script.
+    // The binding code generated by 'attribute SVGMatix foo' in idl requires foo() and updateFoo(),
+    // because SVGTransform.idl needs to return the reference of SVGMatrix.
+    // When JS changes the return value, SVGTransform is applied immediately.
+    // However, CanvanRenderingContext2D doesn't need the implicit update.
+    // So updateCurrentTransform() does nothing.
+    SVGMatrix& currentTransform()
+    {
+        m_dummyCurrentTransform = SVGMatrix(state().m_transform);
+        return m_dummyCurrentTransform;
+    }
+    void updateCurrentTransform() { }
+    void setCurrentTransform(SVGPropertyTearOff<SVGMatrix>*, ExceptionState&);
+
     void scale(float sx, float sy);
     void rotate(float angleInRadians);
     void translate(float tx, float ty);
@@ -330,6 +346,7 @@ private:
     bool m_usesCSSCompatibilityParseMode;
     bool m_hasAlpha;
     MutableStylePropertyMap m_fetchedFonts;
+    SVGMatrix m_dummyCurrentTransform;
 };
 
 } // namespace WebCore