Revert of Consolidate GPU buffer implementations

src/gpu/gl/GrGLTransferBuffer.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 GrGLTransferBuffer_DEFINED
+#define GrGLTransferBuffer_DEFINED
+
+#include "GrTransferBuffer.h"
+#include "GrGLBufferImpl.h"
+#include "gl/GrGLInterface.h"
+
+class GrGLGpu;
+
+class GrGLTransferBuffer : public GrTransferBuffer {
+
+public:
+    typedef GrGLBufferImpl::Desc Desc;
+
+    GrGLTransferBuffer(GrGLGpu* gpu, const Desc& desc, GrGLenum type);
+
+    GrGLuint bufferID() const { return fImpl.bufferID(); }
+    size_t baseOffset() const { return fImpl.baseOffset(); }
+    GrGLenum bufferType() const { return fImpl.bufferType(); }
+
+protected:
+    void onAbandon() override;
+    void onRelease() override;
+    void setMemoryBacking(SkTraceMemoryDump* traceMemoryDump,
+                          const SkString& dumpName) const override;
+
+private:
+    void* onMap() override;
+    void onUnmap() override;
+
+    GrGLGpu* getGpuGL() const {
+        SkASSERT(!this->wasDestroyed());
+        return (GrGLGpu*)(this->getGpu());
+    }
+
+    GrGLBufferImpl fImpl;
+
+    typedef GrTransferBuffer INHERITED;
+};
+
+#endif