Convert readSurfacePixels to use a draw context instead of a texture

src/gpu/gl/GrGLGpu.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrGLGpu.h"
 #include "GrGLBuffer.h"
 #include "GrGLGLSL.h"
@@ skipping 2310 matching lines @@
                                   GrPixelConfig readConfig, DrawPreference* drawPreference,
                                   ReadPixelTempDrawInfo* tempDrawInfo) {
     GrPixelConfig srcConfig = srcSurface->config();
 
     // These settings we will always want if a temp draw is performed.
     tempDrawInfo->fTempSurfaceDesc.fFlags = kRenderTarget_GrSurfaceFlag;
     tempDrawInfo->fTempSurfaceDesc.fWidth = width;
     tempDrawInfo->fTempSurfaceDesc.fHeight = height;
     tempDrawInfo->fTempSurfaceDesc.fSampleCnt = 0;
     tempDrawInfo->fTempSurfaceDesc.fOrigin = kTopLeft_GrSurfaceOrigin; // no CPU y-flip for TL.
-    tempDrawInfo->fUseExactScratch = this->glCaps().partialFBOReadIsSlow();
-
+    tempDrawInfo->fTempSurfaceFit = this->glCaps().partialFBOReadIsSlow() ? SkBackingFit::kExact
+                                                                          : SkBackingFit::kApprox;
     // For now assume no swizzling, we may change that below.
     tempDrawInfo->fSwizzle = GrSwizzle::RGBA();
 
     // Depends on why we need/want a temp draw. Start off assuming no change, the surface we read
     // from will be srcConfig and we will read readConfig pixels from it.
     // Not that if we require a draw and return a non-renderable format for the temp surface the
     // base class will fail for us.
     tempDrawInfo->fTempSurfaceDesc.fConfig = srcConfig;
     tempDrawInfo->fReadConfig = readConfig;
 
@@ skipping 2270 matching lines @@
         if (GR_GL_TEXTURE_EXTERNAL == glTexture->target() ||
             GR_GL_TEXTURE_RECTANGLE == glTexture->target()) {
             copyParams->fFilter = GrTextureParams::kNone_FilterMode;
             copyParams->fWidth = texture->width();
             copyParams->fHeight = texture->height();
             return true;
         }
     }
     return false;
 }