It is dangerous to ignore SkRect::intersect's return value

src/utils/SkGatherPixelRefsAndRects.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkGatherPixelRefsAndRects_DEFINED
 #define SkGatherPixelRefsAndRects_DEFINED
 
@@ skipping 61 matching lines @@
 
         this->drawRect(draw, bounds, paint);
     }
     virtual void drawRect(const SkDraw& draw, const SkRect& rect,
                           const SkPaint& paint) SK_OVERRIDE {
         SkBitmap bm;
         if (GetBitmapFromPaint(paint, &bm)) {
             SkRect mappedRect;
             draw.fMatrix->mapRect(&mappedRect, rect);
             SkRect clipRect = SkRect::Make(draw.fRC->getBounds());
-            mappedRect.intersect(clipRect);
-            fPRCont->add(bm.pixelRef(), mappedRect);
+            if (mappedRect.intersect(clipRect)) {
+                fPRCont->add(bm.pixelRef(), mappedRect);
+            }
         }
     }
     virtual void drawOval(const SkDraw& draw, const SkRect& rect,
                           const SkPaint& paint) SK_OVERRIDE {
         this->drawRect(draw, rect, paint);
     }
     virtual void drawRRect(const SkDraw& draw, const SkRRect& rrect,
                            const SkPaint& paint) SK_OVERRIDE {
         this->drawRect(draw, rrect.rect(), paint);
     }
@@ skipping 215 matching lines @@
     static void NotSupported() {
         SkDEBUGFAIL("this method should never be called");
     }
 
     static void NothingToDo() {}
 
     typedef SkBaseDevice INHERITED;
 };
 
 #endif // SkGatherPixelRefsAndRects_DEFINED