Add mixedtextblob gm and a simple bench

src/gpu/GrAtlasTextContext.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrAtlasTextContext_DEFINED
 #define GrAtlasTextContext_DEFINED
 
@@ skipping 124 matching lines @@
             ::operator delete(target, placement);
         }
     };
 
     typedef BitmapTextBlob::Run Run;
     typedef Run::SubRunInfo PerSubRunInfo;
 
     BitmapTextBlob* CreateBlob(int glyphCount, int runCount);
 
     void appendGlyph(BitmapTextBlob*, int runIndex, GrGlyph::PackedID, int left, int top,
-                     GrFontScaler*, const SkIRect& clipRect);
+                     GrColor color, GrFontScaler*, const SkIRect& clipRect);
     void flush(GrDrawTarget*, BitmapTextBlob*, GrRenderTarget*, const GrPaint&, const GrClip&,
                const SkMatrix& viewMatrix, int paintAlpha);
 
     void internalDrawText(BitmapTextBlob*, int runIndex, SkGlyphCache*, const SkPaint&,
                           const SkMatrix& viewMatrix, const char text[], size_t byteLength,
                           SkScalar x, SkScalar y, const SkIRect& clipRect);
     void internalDrawPosText(BitmapTextBlob*, int runIndex, SkGlyphCache*, const SkPaint&,
                              const SkMatrix& viewMatrix,
                              const char text[], size_t byteLength,
                              const SkScalar pos[], int scalarsPerPosition,
@@ skipping 17 matching lines @@
     // TODO use real cache
     static void ClearCacheEntry(uint32_t key, BitmapTextBlob**);
     SkTHashMap<uint32_t, BitmapTextBlob*, BitmapTextBlob::Hash> fCache;
 
     friend class BitmapTextBatch;
 
     typedef GrTextContext INHERITED;
 };
 
 #endif