Support currentTransform in 2D Canvas.

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index 4d7b8c43d0a40af0aecb4b810b8fecb7bba8f5b4..032730641df98c9d8a13ccd4df0c237250a3731a 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -596,6 +596,16 @@ void CanvasRenderingContext2D::setGlobalCompositeOperation(const String& operati
     c->setCompositeOperation(op, blendMode);
 }
 
+void CanvasRenderingContext2D::setCurrentTransform(SVGPropertyTearOff<SVGMatrix>* currentTransform, ExceptionState& es)
+{
+    if (!currentTransform) {
+        es.throwDOMException(TypeError);
+        return;
+    }
+    const SVGMatrix& matrix = currentTransform->propertyReference();
+    setTransform(matrix.a(), matrix.b(), matrix.c(), matrix.d(), matrix.e(), matrix.f());
+}
+
 void CanvasRenderingContext2D::scale(float sx, float sy)
 {
     GraphicsContext* c = drawingContext();
@@ -698,12 +708,12 @@ void CanvasRenderingContext2D::transform(float m11, float m12, float m21, float
 
     realizeSaves();
 
+    modifiableState().m_transform = newTransform;

[dshwang, 2013/09/20 11:38:52]

when setting non-invertible matrix, currentTransform should keep the value of
non-invertible matrix.

For example,
context.currentTrasform = SVGMatrix(0,0,0,1,0,0);

currentTrasform must be [0,0,0,1,0,0] and the invertible flag of the context
must be set to false.

New layout test covers it.

     if (!newTransform.isInvertible()) {
         modifiableState().m_invertibleCTM = false;
         return;
     }
 
-    modifiableState().m_transform = newTransform;
     c->concatCTM(transform);
     m_path.transform(transform.inverse());
 }