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 b1e34caf093615323edccf25486fdb917ac6c834..7e1592b0fdf930e63606b58a052f45fe85217c61 100644
--- a/Source/platform/graphics/GraphicsContext.cpp
+++ b/Source/platform/graphics/GraphicsContext.cpp
@@ -49,6 +49,7 @@
 #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 +1374,35 @@ void GraphicsContext::clipPath(const Path& pathToClip, WindRule clipRule)
     path.setFillType(previousFillType);
 }
 
+Path GraphicsContext::getCurrentClipPath()
+{
+    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())