Avoid regenerating cached textblobs on integer scrolls

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;
@@ skipping 23 matching lines @@
     cacheBlob->fGlyphIDs =
             reinterpret_cast<GrGlyph::PackedID*>(cacheBlob->fVertices + verticesCount);
     cacheBlob->fRuns = reinterpret_cast<BitmapTextBlob::Run*>(cacheBlob->fGlyphIDs + glyphCount);
 
     // Initialize runs
     for (int i = 0; i < runCount; i++) {
         SkNEW_PLACEMENT(&cacheBlob->fRuns[i], BitmapTextBlob::Run);
     }
     cacheBlob->fRunCount = runCount;
     cacheBlob->fPool = &fPool;
+
+#ifdef SK_DEBUG
+    cacheBlob->fTotalXError = 0;
+    cacheBlob->fTotalYError = 0;
+#endif
     return cacheBlob;
 }