Implement basic parts of hit regions on canvas2d.

Source/platform/graphics/GraphicsContext.cpp

Index: Source/platform/graphics/GraphicsContext.cpp
diff --git a/Source/platform/graphics/GraphicsContext.cpp b/Source/platform/graphics/GraphicsContext.cpp
index 9b479b7a2bae3d42b7859d453cacbbd1e6fec725..749bc941457c06b4fa8910842d33193c8a19a485 100644
--- a/Source/platform/graphics/GraphicsContext.cpp
+++ b/Source/platform/graphics/GraphicsContext.cpp
@@ -38,6 +38,7 @@
 #include "platform/text/TextRunIterator.h"
 #include "platform/weborigin/KURL.h"
 #include "third_party/skia/include/core/SkAnnotation.h"
+#include "third_party/skia/include/core/SkClipStack.h"
 #include "third_party/skia/include/core/SkColorFilter.h"
 #include "third_party/skia/include/core/SkData.h"
 #include "third_party/skia/include/core/SkDevice.h"
@@ -1373,6 +1374,14 @@ void GraphicsContext::clipPath(const Path& pathToClip, WindRule clipRule)
     path.setFillType(previousFillType);
 }
 
+bool GraphicsContext::isClipMode() const
+{
+    if (contextDisabled())
+        return false;
+
+    return m_canvas->getClipStack()->getSaveCount() != 0;
+}
+
 void GraphicsContext::clipConvexPolygon(size_t numPoints, const FloatPoint* points, bool antialiased)
 {
     if (contextDisabled())