Add transfer buffer support.

src/gpu/gl/GrGLGpu.h

Index: src/gpu/gl/GrGLGpu.h
diff --git a/src/gpu/gl/GrGLGpu.h b/src/gpu/gl/GrGLGpu.h
index 637a1cf16157af0a0b95f7802f181e6525b179fc..9203d117fa5dfaa2700739f11c6c355e4da9674b 100644
--- a/src/gpu/gl/GrGLGpu.h
+++ b/src/gpu/gl/GrGLGpu.h
@@ -16,6 +16,7 @@
 #include "GrGLRenderTarget.h"
 #include "GrGLStencilAttachment.h"
 #include "GrGLTexture.h"
+#include "GrGLTransferBuffer.h"
 #include "GrGLVertexArray.h"
 #include "GrGLVertexBuffer.h"
 #include "GrGpu.h"
@@ -101,12 +102,12 @@ public:
     void releaseBuffer(GrGLuint id, GrGLenum type);
 
     // sizes are in bytes
-    void* mapBuffer(GrGLuint id, GrGLenum type, bool dynamic, size_t currentSize,
+    void* mapBuffer(GrGLuint id, GrGLenum type, GrGLBufferImpl::Usage usage, size_t currentSize,
                     size_t requestedSize);
 
     void unmapBuffer(GrGLuint id, GrGLenum type, void* mapPtr);
 
-    void bufferData(GrGLuint id, GrGLenum type, bool dynamic, size_t currentSize,
+    void bufferData(GrGLuint id, GrGLenum type, GrGLBufferImpl::Usage usage, size_t currentSize,
                     const void* src, size_t srcSizeInBytes);
 
     const GrGLContext* glContextForTesting() const override {
@@ -143,6 +144,7 @@ private:
                                          const void* srcData) override;
     GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) override;
     GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) override;
+    GrTransferBuffer* onCreateTransferBuffer(size_t size, bool toGpu) override;
     GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) override;
     GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                               GrWrapOwnership) override;