Work around for nexus 6 TexSubImage issue

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 64f4cb3deca237649047db0ababf9954813ca01e..3c25f3d1a9a986ff2e135767f31e2b74d0b102e3 100755
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -324,7 +324,9 @@ bool GrContext::writeSurfacePixels(GrSurface* surface,
     {
         GrTexture* texture = NULL;
         if (!(kUnpremul_PixelOpsFlag & pixelOpsFlags) && (texture = surface->asTexture()) &&
-            fGpu->canWriteTexturePixels(texture, srcConfig)) {
+            fGpu->canWriteTexturePixels(texture, srcConfig) &&
+            (!fCaps->useDrawInsteadOfPartialRenderTargetWrite() || !surface->asRenderTarget() ||
+              (width == texture->width() && height == texture->height()))) {
 
             if (!(kDontFlush_PixelOpsFlag & pixelOpsFlags) &&
                 surface->surfacePriv().hasPendingIO()) {