Fix 'i-i' to 'i-1' in SkCanvasStack.

src/utils/SkCanvasStack.cpp

 
 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkCanvasStack.h"
 
 SkCanvasStack::SkCanvasStack(int width, int height)
@@ skipping 17 matching lines @@
         data->requiredClip.setRect(canvasBounds);
 
         // subtract this region from the canvas objects already on the stack.
         // This ensures they do not draw into the space occupied by the layers
         // above them.
         for (int i = fList.count() - 1; i > 0; --i) {
             SkIRect localBounds = canvasBounds;
             localBounds.offset(origin - fCanvasData[i-1].origin);
 
             fCanvasData[i-1].requiredClip.op(localBounds, SkRegion::kDifference_Op);
-            fList[i-i]->clipRegion(fCanvasData[i-1].requiredClip);
+            fList[i-1]->clipRegion(fCanvasData[i-1].requiredClip);
         }
     }
     SkASSERT(fList.count() == fCanvasData.count());
 }
 
 void SkCanvasStack::removeAll() {
     fCanvasData.reset();
     this->INHERITED::removeAll();
 }
 
@@ skipping 50 matching lines @@
     SkASSERT(fList.count() == fCanvasData.count());
     for (int i = 0; i < fList.count(); ++i) {
         SkRegion tempRegion;
         deviceRgn.translate(-fCanvasData[i].origin.x(),
                             -fCanvasData[i].origin.y(), &tempRegion);
         tempRegion.op(fCanvasData[i].requiredClip, SkRegion::kIntersect_Op);
         fList[i]->clipRegion(tempRegion, op);
     }
     return this->SkCanvas::clipRegion(deviceRgn, op);
 }