Use texture strip atlas for color table filter

src/gpu/effects/GrTextureStripAtlas.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTextureStripAtlas_DEFINED
 #define GrTextureStripAtlas_DEFINED
 
@@ skipping 43 matching lines @@
      *
      * If a regular texture access without using the atlas looks like:
      *
      *      texture2D(sampler, vec2(x, y))
      *
      * Then when using the atlas we'd replace it with:
      *
      *       texture2D(sampler, vec2(x, yOffset + y * scaleFactor))
      *
      * Where yOffset, returned by getYOffset(), is the offset to the start of the row within the
-     * atlas and scaleFactor, returned by getVerticalScaleFactor(), is the y-scale of the row,
-     * relative to the height of the overall atlas texture.
+     * atlas and scaleFactor, returned by getNormalizedTexelHeight, is the normalized height of
+     * one texel row.
      */
     SkScalar getYOffset(int row) const { return SkIntToScalar(row) / fNumRows; }
-    SkScalar getVerticalScaleFactor() const { return SkIntToScalar(fDesc.fRowHeight) / fDesc.fHeight; }
+    SkScalar getNormalizedTexelHeight() const { return fNormalizedYHeight; }
 
     GrContext* getContext() const { return fDesc.fContext; }
     GrTexture* getTexture() const { return fTexture; }
 
 private:
 
     // Key to indicate an atlas row without any meaningful data stored in it
     const static uint32_t kEmptyAtlasRowKey = 0xffffffff;
 
     /**
@@ skipping 82 matching lines @@
     // get a texture back from the texture cache, that it's the same one we last used.
     const int32_t fCacheKey;
 
     // Total locks on all rows (when this reaches zero, we can unlock our texture)
     int32_t fLockedRows;
 
     const Desc fDesc;
     const uint16_t fNumRows;
     GrTexture* fTexture;
 
+    SkScalar fNormalizedYHeight;
+
     // Array of AtlasRows which store the state of all our rows. Stored in a contiguous array, in
     // order that they appear in our texture, this means we can subtract this pointer from a row
     // pointer to get its index in the texture, and can save storing a row number in AtlasRow.
     AtlasRow* fRows;
 
     // Head and tail for linked list of least-recently-used rows (front = least recently used).
     // Note that when a texture is locked, it gets removed from this list until it is unlocked.
     AtlasRow* fLRUFront;
     AtlasRow* fLRUBack;
 
     // A list of pointers to AtlasRows that currently contain cached images, sorted by key
     SkTDArray<AtlasRow*> fKeyTable;
 };
 
 #endif