Convert readSurfacePixels to use a draw context instead of a texture

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 152 matching lines @@
 
     /** 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. */
         GrSurfaceDesc   fTempSurfaceDesc;
         /** Indicates whether there is a performance advantage to using an exact match texture
             (in terms of width and height) for the intermediate texture instead of approximate. */
-        bool            fUseExactScratch;
+        SkBackingFit    fTempSurfaceFit;
         /** Swizzle to apply during the draw. This is used to compensate for either feature or
             performance limitations in the underlying 3D API. */
         GrSwizzle       fSwizzle;
         /** The config that should be used to read from the temp surface after the draw. This may be
             different than the original read config in order to compensate for swizzling. The
             read data will effectively be in the original read config. */
         GrPixelConfig   fReadConfig;
     };
 
     /** Describes why an intermediate draw must/should be performed before readPixels. */
@@ skipping 414 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