add isRect() check to AAClip, to detect if a soft-clip is really just an irect

src/core/SkAAClip.h

Index: src/core/SkAAClip.h
diff --git a/src/core/SkAAClip.h b/src/core/SkAAClip.h
index f2cde62dbc8d90387a83fe4ff806fb60ea49bfc5..c36a3e98ce734d1ce1096edc244034372ba91403 100644
--- a/src/core/SkAAClip.h
+++ b/src/core/SkAAClip.h
@@ -29,6 +29,10 @@ public:
     bool isEmpty() const { return NULL == fRunHead; }
     const SkIRect& getBounds() const { return fBounds; }
 
+    // Returns true iff the clip is not empty, and is just a hard-edged rect (no partial alpha).
+    // If true, getBounds() can be used in place of this clip.
+    bool isRect() const;
+
     bool setEmpty();
     bool setRect(const SkIRect&);
     bool setRect(const SkRect&, bool doAA = true);