small fix for perf regression in GrAtlasTextContext

src/gpu/GrBatchAtlas.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrBatchAtlas.h"
 #include "GrBatchTarget.h"
 #include "GrGpu.h"
@@ skipping 348 matching lines @@
 
 void GrBatchAtlas::setLastUseToken(AtlasID id, BatchToken batchToken) {
     SkASSERT(this->hasID(id));
     int index = GetIndexFromID(id);
     SkASSERT(index < fNumPlotsX * fNumPlotsY);
     this->makeMRU(fPlotArray[index]);
     fPlotArray[index]->setLastUseToken(batchToken);
 }
 
 void GrBatchAtlas::setLastUseTokenBulk(const BulkUseTokenUpdater& updater, BatchToken batchToken) {
-    for (int i = 0; i < updater.fCount; i++) {
+    int count = updater.fPlotsToUpdate.count();
+    for (int i = 0; i < count; i++) {
         BatchPlot* plot = fPlotArray[updater.fPlotsToUpdate[i]];
         this->makeMRU(plot);
         plot->setLastUseToken(batchToken);
     }
 }