Add sanity check to GrAtlasTextBlob

src/gpu/GrTextBlobCache.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 "GrTextBlobCache.h"
 
 static const int kVerticesPerGlyph = 4;
 
 GrTextBlobCache::~GrTextBlobCache() {
     this->freeAll();
 }
 
-GrAtlasTextBlob* GrTextBlobCache::createBlob(int glyphCount, int runCount,
-                                                                size_t maxVASize) {
+GrAtlasTextBlob* GrTextBlobCache::createBlob(int glyphCount, int runCount, size_t maxVASize) {
     // We allocate size for the GrAtlasTextBlob itself, plus size for the vertices array,
     // and size for the glyphIds array.
     size_t verticesCount = glyphCount * kVerticesPerGlyph * maxVASize;
     size_t size = sizeof(GrAtlasTextBlob) +
                   verticesCount +
                   glyphCount * sizeof(GrGlyph**) +
                   sizeof(GrAtlasTextBlob::Run) * runCount;
 
-    GrAtlasTextBlob* cacheBlob = SkNEW_PLACEMENT(fPool.allocate(size), GrAtlasTextBlob);
+    void* allocation = fPool.allocate(size);
+#ifdef CACHE_SANITY_CHECK
+    sk_bzero(allocation, size);
+#endif
+
+    GrAtlasTextBlob* cacheBlob = SkNEW_PLACEMENT(allocation, GrAtlasTextBlob);
+#ifdef CACHE_SANITY_CHECK
+    cacheBlob->fSize = size;
+#endif
 
     // setup offsets for vertices / glyphs
     cacheBlob->fVertices = sizeof(GrAtlasTextBlob) + reinterpret_cast<unsigned char*>(cacheBlob);
     cacheBlob->fGlyphs = reinterpret_cast<GrGlyph**>(cacheBlob->fVertices + verticesCount);
     cacheBlob->fRuns = reinterpret_cast<GrAtlasTextBlob::Run*>(cacheBlob->fGlyphs + glyphCount);
 
     // Initialize runs
     for (int i = 0; i < runCount; i++) {
         SkNEW_PLACEMENT(&cacheBlob->fRuns[i], GrAtlasTextBlob::Run);
     }
     cacheBlob->fRunCount = runCount;
     cacheBlob->fPool = &fPool;
     return cacheBlob;
 }
 
 void GrTextBlobCache::freeAll() {
     SkTDynamicHash<GrAtlasTextBlob, GrAtlasTextBlob::Key>::Iter iter(&fCache);
     while (!iter.done()) {
         GrAtlasTextBlob* blob = &(*iter);
         fBlobList.remove(blob);
         blob->unref();
         ++iter;
     }
     fCache.rewind();
 }