Use transfer buffer for BatchAtlas texture copies

src/gpu/gl/GrGLBuffer.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLBuffer.h"
 #include "GrGLGpu.h"
 #include "SkTraceMemoryDump.h"
@@ skipping 12 matching lines @@
 #endif
 
 #ifdef SK_DEBUG
 #define VALIDATE() this->validate()
 #else
 #define VALIDATE() do {} while(false)
 #endif
 
 GrGLBuffer* GrGLBuffer::Create(GrGLGpu* gpu, size_t size, GrBufferType intendedType,
                                GrAccessPattern accessPattern, const void* data) {
+    if (gpu->glCaps().transferBufferType() == GrGLCaps::kNone_TransferBufferType &&
+        (kXferCpuToGpu_GrBufferType == intendedType ||
+         kXferGpuToCpu_GrBufferType == intendedType)) {
+        return nullptr;
+    }
+    
     bool cpuBacked = gpu->glCaps().useNonVBOVertexAndIndexDynamicData() &&
                      GrBufferTypeIsVertexOrIndex(intendedType) &&
                      kDynamic_GrAccessPattern == accessPattern;
     SkAutoTUnref<GrGLBuffer> buffer(new GrGLBuffer(gpu, size, intendedType, accessPattern,
                                                    cpuBacked, data));
     if (!cpuBacked && 0 == buffer->bufferID()) {
         return nullptr;
     }
     return buffer.release();
 }
@@ skipping 274 matching lines @@
 
 void GrGLBuffer::validate() const {
     // The following assert isn't valid when the buffer has been abandoned:
     // SkASSERT((0 == fDesc.fID) == (fCPUData));
     SkASSERT(0 != fBufferID || 0 == fGLSizeInBytes);
     SkASSERT(nullptr == fMapPtr || fCPUData || fGLSizeInBytes <= fSizeInBytes);
     SkASSERT(nullptr == fCPUData || nullptr == fMapPtr || fCPUData == fMapPtr);
 }
 
 #endif