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 46107a2e2a63580559d3bda1e19eb487bc481769..8b1ada1935729b5b22e13193ef4f431e39b682d6 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.h
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.h
@@ -57,6 +57,7 @@ class HTMLImageElement;
 class HTMLVideoElement;
 class ImageBitmap;
 class ImageData;
+class SVGMatrix;
 class TextMetrics;
 
 typedef HashMap<String, RefPtr<MutableStylePropertySet> > MutableStylePropertyMap;
@@ -117,6 +118,8 @@ public:
     void save() { ++m_unrealizedSaveCount; }
     void restore();
 
+    SVGMatrix currentTransform() const;

[Justin Novosad, 2013/09/19 19:23:48]

IIRC, you can't return an incomplete type.  If this code compiles as is, you
probably don't need the above forward declaration. Also, it is returning by
value, which may not be the best thing to do here.  Maybe you could make this
function an inline so that the compiler can optimize-out the transient copy of
the return value. http://en.wikipedia.org/wiki/Return_value_optimization

+    void setCurrentTransform(const SVGMatrix&);
     void scale(float sx, float sy);
     void rotate(float angleInRadians);
     void translate(float tx, float ty);