Avoid regenerating cached textblobs on integer scrolls

src/gpu/GrTextBlobCache.cpp

Index: src/gpu/GrTextBlobCache.cpp
diff --git a/src/gpu/GrTextBlobCache.cpp b/src/gpu/GrTextBlobCache.cpp
index 9141b1712ad67c26c3f32360bb3dd01dc3208b37..a5ef07c9f6c6c22a5d141abc6d8e704b7452219b 100644
--- a/src/gpu/GrTextBlobCache.cpp
+++ b/src/gpu/GrTextBlobCache.cpp
@@ -41,5 +41,10 @@ GrAtlasTextContext::BitmapTextBlob* GrTextBlobCache::createBlob(int glyphCount,
     }
     cacheBlob->fRunCount = runCount;
     cacheBlob->fPool = &fPool;
+
+#ifdef SK_DEBUG
+    cacheBlob->fTotalXError = 0;
+    cacheBlob->fTotalYError = 0;
+#endif
     return cacheBlob;
 }