Adding a cache + memory pool for GPU TextBlobs

include/core/SkTextBlob.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkTextBlob_DEFINED
 #define SkTextBlob_DEFINED
 
@@ skipping 74 matching lines @@
     void operator delete(void* p) { sk_free(p); }
     void* operator new(size_t) {
         SkFAIL("All blobs are created by placement new.");
         return sk_malloc_throw(0);
     }
     void* operator new(size_t, void* p) { return p; }
 
     static unsigned ScalarsPerGlyph(GlyphPositioning pos);
 
     friend class GrAtlasTextContext;
+    friend class GrTextBlobCache;
     friend class GrTextContext;
     friend class SkBaseDevice;
     friend class SkTextBlobBuilder;
     friend class TextBlobTester;
 
     const int        fRunCount;
     const SkRect     fBounds;
     const uint32_t fUniqueID;
 
     SkDEBUGCODE(size_t fStorageSize;)
@@ skipping 94 matching lines @@
 
     SkRect                 fBounds;
     int                    fRunCount;
     bool                   fDeferredBounds;
     size_t                 fLastRun; // index into fStorage
 
     RunBuffer              fCurrentRunBuffer;
 };
 
 #endif // SkTextBlob_DEFINED