Work around for nexus 6 TexSubImage issue

include/gpu/GrContextOptions.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 GrContextOptions_DEFINED
 #define GrContextOptions_DEFINED
 
 #include "SkTypes.h"
 
 struct GrContextOptions {
     GrContextOptions()
         : fDrawPathToCompressedTexture(false)
         , fSuppressPrints(false)
         , fMaxTextureSizeOverride(SK_MaxS32)
         , fMinTextureSizeOverride(0)
         , fSuppressDualSourceBlending(false)
-        , fGeometryBufferMapThreshold(-1) {}
+        , fGeometryBufferMapThreshold(-1)
+        , fUseDrawInsteadOfPartialRenderTargetWrite(false) {}
 
     // EXPERIMENTAL
     // May be removed in the future, or may become standard depending
     // on the outcomes of a variety of internal tests.
     bool fDrawPathToCompressedTexture;
 
     // Suppress prints for the GrContext.
     bool fSuppressPrints;
 
     /** Overrides: These options override feature detection using backend API queries. These
         overrides can only reduce the feature set or limits, never increase them beyond the
         detected values. */
 
     int  fMaxTextureSizeOverride;
     int  fMinTextureSizeOverride;
     bool fSuppressDualSourceBlending;
 
     /** the threshold in bytes above which we will use a buffer mapping API to map vertex and index
         buffers to CPU memory in order to update them.  A value of -1 means the GrContext should
         deduce the optimal value for this platform. */
     int  fGeometryBufferMapThreshold;
+
+    /** some gpus have problems with partial writes of the rendertarget */
+    bool fUseDrawInsteadOfPartialRenderTargetWrite;
 };
 
 #endif