Avoid some work on SkClipStack equality when the topmost genids match

src/core/SkClipStack.cpp

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkClipStack.h"
 #include "SkPath.h"
 #include "SkThread.h"
@@ skipping 388 matching lines @@
     for (const Element* element = (const Element*)recIter.next();
          element != NULL;
          element = (const Element*)recIter.next()) {
         new (fDeque.push_back()) Element(*element);
     }
 
     return *this;
 }
 
 bool SkClipStack::operator==(const SkClipStack& b) const {
+    if (this->getTopmostGenID() == b.getTopmostGenID()) {
+        return true;
+    }
     if (fSaveCount != b.fSaveCount ||
         fDeque.count() != b.fDeque.count()) {
         return false;
     }
     SkDeque::F2BIter myIter(fDeque);
     SkDeque::F2BIter bIter(b.fDeque);
     const Element* myElement = (const Element*)myIter.next();
     const Element* bElement = (const Element*)bIter.next();
 
     while (myElement != NULL && bElement != NULL) {
@@ skipping 308 matching lines @@
         return kWideOpenGenID;
     }
 
     const Element* back = static_cast<const Element*>(fDeque.back());
     if (kInsideOut_BoundsType == back->fFiniteBoundType && back->fFiniteBound.isEmpty()) {
         return kWideOpenGenID;
     }
 
     return back->getGenID();
 }