fix a bug in scrolling BitmapText gpu cached textblobs

src/gpu/GrAtlasTextContext.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 "GrAtlasTextContext.h"
 
 #include "GrAtlas.h"
 #include "GrBatch.h"
@@ skipping 289 matching lines @@
         // This cool bit of math will determine the necessary translation to apply to the already
         // generated vertex coordinates to move them to the correct position
         SkScalar transX = viewMatrix.getTranslateX() +
                           viewMatrix.getScaleX() * (x - blob.fX) +
                           viewMatrix.getSkewX() * (y - blob.fY) -
                           blob.fViewMatrix.getTranslateX();
         SkScalar transY = viewMatrix.getTranslateY() +
                           viewMatrix.getSkewY() * (x - blob.fX) +
                           viewMatrix.getScaleY() * (y - blob.fY) -
                           blob.fViewMatrix.getTranslateY();
-        if (SkScalarFraction(transX) > SK_ScalarNearlyZero ||
-            SkScalarFraction(transY) > SK_ScalarNearlyZero) {
+        if (!SkScalarIsInt(transX) || !SkScalarIsInt(transY) ) {
             return true;
         }
 
-#ifdef SK_DEBUG
-        static const SkScalar kMinDiscernableTranslation = 0.0625;
-        // As a safeguard when debugging, we store the total error across all translations and print
-        // if the error becomes discernable.  This is pretty unlikely to occur given the tight
-        // bounds above on translation
-        blob.fTotalXError += SkScalarAbs(SkScalarFraction(transX));
-        blob.fTotalYError += SkScalarAbs(SkScalarFraction(transY));
-        if (blob.fTotalXError > kMinDiscernableTranslation ||
-            blob.fTotalYError > kMinDiscernableTranslation) {
-            SkDebugf("Exceeding error threshold for bitmap text translation");
-        }
-#endif
         (*outTransX) = transX;
         (*outTransY) = transY;
     } else if (blob.hasDistanceField()) {
         // A scale outside of [blob.fMaxMinScale, blob.fMinMaxScale] would result in a different
         // distance field being generated, so we have to regenerate in those cases
         SkScalar newMaxScale = viewMatrix.getMaxScale();
         SkScalar oldMaxScale = blob.fViewMatrix.getMaxScale();
         SkScalar scaleAdjust = newMaxScale / oldMaxScale;
         if (scaleAdjust < blob.fMaxMinScale || scaleAdjust > blob.fMinMaxScale) {
             return true;
@@ skipping 1832 matching lines @@
     pipelineBuilder.setFromPaint(grPaint, rt, clip);
 
     GrColor color = grPaint.getColor();
     for (int run = 0; run < cacheBlob->fRunCount; run++) {
         this->flushRun(target, &pipelineBuilder, cacheBlob, run, color, 0, 0, skPaint);
     }
 
     // Now flush big glyphs
     this->flushBigGlyphs(cacheBlob, rt, grPaint, clip, 0, 0);
 }