Add some copy support for vulkan msaa

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 290 matching lines @@
      * @param offset           offset from the start of the buffer
      * @param rowBytes         number of bytes between consecutive rows. Zero
      *                         means rows are tightly packed.
      */
     bool transferPixels(GrSurface* surface,
                         int left, int top, int width, int height,
                         GrPixelConfig config, GrBuffer* transferBuffer,
                         size_t offset, size_t rowBytes);
 
     /**
-     * This is can be called before allocating a texture to be a dst for copySurface. It will
+     * This is can be called before allocating a texture to be a dst for copySurface. This is only
+     * used for doing dst copies needed in blends, thus the src is always a GrRenderTarget. It will
      * populate the origin, config, and flags fields of the desc such that copySurface can
-     * efficiently succeed. It should only succeed if it can allow copySurface to perform a copy
-     * that would be more effecient than drawing the src to a dst render target.
+     * efficiently succeed.
      */
-    virtual bool initCopySurfaceDstDesc(const GrSurface* src, GrSurfaceDesc* desc) const = 0;
+    virtual bool initDescForDstCopy(const GrRenderTarget* src, GrSurfaceDesc* desc) const = 0;
 
     // After the client interacts directly with the 3D context state the GrGpu
     // must resync its internal state and assumptions about 3D context state.
     // Each time this occurs the GrGpu bumps a timestamp.
     // state of the 3D context
     // At 10 resets / frame and 60fps a 64bit timestamp will overflow in about
     // a billion years.
     typedef uint64_t ResetTimestamp;
 
     // This timestamp is always older than the current timestamp
@@ skipping 271 matching lines @@
     SkSTArray<1, MultisampleSpecs, true>   fMultisampleSpecs;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by Gpu.
     GrContext*                             fContext;
 
     friend class GrPathRendering;
     friend class gr_instanced::InstancedRendering;
     typedef SkRefCnt INHERITED;
 };
 
 #endif