Change implementation of flush-count based GrGpuResource purging

src/gpu/GrGpuResource.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 "GrGpuResource.h"
 #include "GrContext.h"
 #include "GrResourceCache.h"
 #include "GrGpu.h"
 #include "GrGpuResourcePriv.h"
 #include "SkTraceMemoryDump.h"
 
 static inline GrResourceCache* get_resource_cache(GrGpu* gpu) {
     SkASSERT(gpu);
     SkASSERT(gpu->getContext());
     SkASSERT(gpu->getContext()->getResourceCache());
     return gpu->getContext()->getResourceCache();
 }
 
 GrGpuResource::GrGpuResource(GrGpu* gpu)
-    : fGpu(gpu)
+    : fExternalFlushCntWhenBecamePurgeable(0)
+    , fGpu(gpu)
     , fGpuMemorySize(kInvalidGpuMemorySize)
     , fBudgeted(SkBudgeted::kNo)
     , fRefsWrappedObjects(false)
     , fUniqueID(CreateUniqueID()) {
     SkDEBUGCODE(fCacheArrayIndex = -1);
 }
 
 void GrGpuResource::registerWithCache(SkBudgeted budgeted) {
     SkASSERT(fBudgeted == SkBudgeted::kNo);
     fBudgeted = budgeted;
@@ skipping 160 matching lines @@
 }
 
 uint32_t GrGpuResource::CreateUniqueID() {
     static int32_t gUniqueID = SK_InvalidUniqueID;
     uint32_t id;
     do {
         id = static_cast<uint32_t>(sk_atomic_inc(&gUniqueID) + 1);
     } while (id == SK_InvalidUniqueID);
     return id;
 }