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..1f353c85ad02523a01b809a50e934f507a427b03 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"
@@ -50,6 +51,7 @@
 #include "third_party/skia/include/effects/SkLumaColorFilter.h"
 #include "third_party/skia/include/gpu/GrRenderTarget.h"
 #include "third_party/skia/include/gpu/GrTexture.h"
+#include "third_party/skia/include/pathops/SkPathOps.h"
 #include "wtf/Assertions.h"
 #include "wtf/MathExtras.h"
 
@@ -1373,6 +1375,43 @@ 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;
+}
+
+Path GraphicsContext::getCurrentClipPath() const
+{
+    if (contextDisabled())
+        return Path();
+
+    const SkClipStack* clipStack = m_canvas->getClipStack();
+    SkClipStack::Iter iter(*clipStack, SkClipStack::Iter::kBottom_IterStart);
+    const SkClipStack::Element* element;
+
+    SkPath totalClipPath;
+    totalClipPath.setFillType(SkPath::kInverseEvenOdd_FillType);
+
+    while ((element = iter.next())) {
+
+        SkClipStack::Element::Type type = element->getType();
+        SkPath clipPath;
+        if (type != SkClipStack::Element::kEmpty_Type)
+            element->asPath(&clipPath);
+
+        SkRegion::Op elementOp = element->getOp();
+        if (elementOp == SkRegion::kReplace_Op)
+            totalClipPath = clipPath;
+        else
+            Op(totalClipPath, clipPath, (SkPathOp)elementOp, &totalClipPath);
+    }
+
+    return Path(totalClipPath);
+}
+
 void GraphicsContext::clipConvexPolygon(size_t numPoints, const FloatPoint* points, bool antialiased)
 {
     if (contextDisabled())