Add transfer buffer support.

src/gpu/GrGpu.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGpu_DEFINED
 #define GrGpu_DEFINED
 
@@ skipping 13 matching lines @@
 class GrPathRange;
 class GrPathRenderer;
 class GrPathRendererChain;
 class GrPathRendering;
 class GrPipeline;
 class GrPrimitiveProcessor;
 class GrRenderTarget;
 class GrStencilAttachment;
 class GrSurface;
 class GrTexture;
+class GrTransferBuffer;
 class GrVertexBuffer;
 class GrVertices;
 
 class GrGpu : public SkRefCnt {
 public:
     /**
      * Create an instance of GrGpu that matches the specified backend. If the requested backend is
      * not supported (at compile-time or run-time) this returns nullptr. The context will not be
      * fully constructed and should not be used by GrGpu until after this function returns.
      */
@@ skipping 78 matching lines @@
      * @param size    size in bytes of the index buffer
      * @param dynamic hints whether the data will be frequently changed
      *                by either GrIndexBuffer::map() or
      *                GrIndexBuffer::updateData().
      *
      * @return The index buffer if successful, otherwise nullptr.
      */
     GrIndexBuffer* createIndexBuffer(size_t size, bool dynamic);
 
     /**
+     * Creates a transfer buffer.
+     *
+     * @param size      size in bytes of the index buffer
+     * @param toGpu     true if used to transfer from the cpu to the gpu

[bsalomon, 2015/12/02 16:38:31]

Maybe an enum instead of a bool for clarity at the call sites? something like

enum {
kCpuToGpu_TransferType
kGpuToGpu_TransferType
};

[jvanverth1, 2015/12/02 18:05:07]

Done.

+     *                  otherwise to be used to transfer from the gpu to the cpu
+     *
+     * @return The transfer buffer if successful, otherwise nullptr.
+     */
+    GrTransferBuffer* createTransferBuffer(size_t size, bool toGpu);
+    
+    /**
      * Resolves MSAA.
      */
     void resolveRenderTarget(GrRenderTarget* target);
 
     /** Info struct returned by getReadPixelsInfo about performing intermediate draws before
         reading pixels for performance or correctness. */
     struct ReadPixelTempDrawInfo {
         /** If the GrGpu is requesting that the caller do a draw to an intermediate surface then
             this is descriptor for the temp surface. The draw should always be a rect with
             dst 0,0,w,h. */
@@ skipping 301 matching lines @@
                                        GrGpuResource::LifeCycle lifeCycle,
                                        const void* srcData, size_t rowBytes) = 0;
     virtual GrTexture* onCreateCompressedTexture(const GrSurfaceDesc& desc,
                                                  GrGpuResource::LifeCycle lifeCycle,
                                                  const void* srcData) = 0;
     virtual GrTexture* onWrapBackendTexture(const GrBackendTextureDesc&, GrWrapOwnership) = 0;
     virtual GrRenderTarget* onWrapBackendRenderTarget(const GrBackendRenderTargetDesc&,
                                                       GrWrapOwnership) = 0;
     virtual GrVertexBuffer* onCreateVertexBuffer(size_t size, bool dynamic) = 0;
     virtual GrIndexBuffer* onCreateIndexBuffer(size_t size, bool dynamic) = 0;
+    virtual GrTransferBuffer* onCreateTransferBuffer(size_t size, bool toGpu) = 0;
 
     // overridden by backend-specific derived class to perform the clear.
     virtual void onClear(GrRenderTarget*, const SkIRect& rect, GrColor color) = 0;
 
 
     // Overridden by backend specific classes to perform a clear of the stencil clip bits.  This is
     // ONLY used by the the clip target
     virtual void onClearStencilClip(GrRenderTarget*, const SkIRect& rect, bool insideClip) = 0;
 
     // overridden by backend-specific derived class to perform the draw call.
@@ skipping 38 matching lines @@
     ResetTimestamp                                                      fResetTimestamp;
     uint32_t                                                            fResetBits;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
     GrContext*                                                          fContext;
 
     friend class GrPathRendering;
     typedef SkRefCnt INHERITED;
 };
 
 #endif