Use SkPathRef gen id for SkPath::getGenerationID

src/core/SkPathRef.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 "SkBuffer.h"
 #include "SkOnce.h"
 #include "SkPath.h"
@@ skipping 271 matching lines @@
     this->fVerbs[~fVerbCnt] = verb;
     SkPoint* ret = fPoints + fPointCnt;
     fVerbCnt += 1;
     fPointCnt += pCnt;
     fFreeSpace -= space;
     fBoundsIsDirty = true;  // this also invalidates fIsFinite
     SkDEBUGCODE(this->validate();)
     return ret;
 }
 
-int32_t SkPathRef::genID() const {
+uint32_t SkPathRef::genID() const {
     SkASSERT(!fEditorsAttached);
+    static const uint32_t kMask = (static_cast<int64_t>(1) << SkPath::kPathRefGenIDBitCnt) - 1;
     if (!fGenerationID) {
         if (0 == fPointCnt && 0 == fVerbCnt) {
             fGenerationID = kEmptyGenID;
         } else {
             static int32_t  gPathRefGenerationID;
             // do a loop in case our global wraps around, as we never want to return a 0 or the
             // empty ID
             do {
-                fGenerationID = sk_atomic_inc(&gPathRefGenerationID) + 1;
+                fGenerationID = (sk_atomic_inc(&gPathRefGenerationID) + 1) & kMask;
             } while (fGenerationID <= kEmptyGenID);
         }
     }
     return fGenerationID;
 }
 
 #ifdef SK_DEBUG
 void SkPathRef::validate() const {
     this->INHERITED::validate();
     SkASSERT(static_cast<ptrdiff_t>(fFreeSpace) >= 0);
@@ skipping 16 matching lines @@
                      fPoints[i].fY - fBounds.fBottom < SK_ScalarNearlyZero);
             if (!fPoints[i].isFinite()) {
                 isFinite = false;
             }
         }
         SkASSERT(SkToBool(fIsFinite) == isFinite);
     }
 #endif
 }
 #endif