Avoid re-rendering stencil clip for every draw with reducable clip stack

src/gpu/GrStencilBuffer.h

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrStencilBuffer_DEFINED
@@ skipping 25 matching lines @@
                      const SkIPoint clipSpaceToStencilOffset) {
         fLastClipStackGenID = clipStackGenID;
         fLastClipStackRect = clipSpaceRect;
         fLastClipSpaceOffset = clipSpaceToStencilOffset;
     }
 
     // called to determine if we have to render the clip into SB.
     bool mustRenderClip(int32_t clipStackGenID,
                         const SkIRect& clipSpaceRect,
                         const SkIPoint clipSpaceToStencilOffset) const {
-        return SkClipStack::kInvalidGenID == clipStackGenID ||
-               fLastClipStackGenID != clipStackGenID ||
+        return fLastClipStackGenID != clipStackGenID ||
                fLastClipSpaceOffset != clipSpaceToStencilOffset ||
                !fLastClipStackRect.contains(clipSpaceRect);
     }
 
     // Places the sb in the cache. The cache takes a ref of the stencil buffer.
     void transferToCache();
 
     static GrResourceKey ComputeKey(int width, int height, int sampleCnt);
 
 protected:
@@ skipping 15 matching lines @@
     int fSampleCnt;
 
     int32_t     fLastClipStackGenID;
     SkIRect     fLastClipStackRect;
     SkIPoint    fLastClipSpaceOffset;
 
     typedef GrResource INHERITED;
 };
 
 #endif