Move prepareForExternalIO from GrRenderTarget to GrDrawContext

include/gpu/GrDrawContext.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDrawContext_DEFINED
 #define GrDrawContext_DEFINED
 
@@ skipping 235 matching lines @@
      *  - The sides (along the shrink axis) and center are not drawn
      */
     void drawImageNine(const GrClip&,
                        const GrPaint& paint,
                        const SkMatrix& viewMatrix,
                        int imageWidth,
                        int imageHeight,
                        const SkIRect& center,
                        const SkRect& dst);
 
+    /**
+     * After this returns any pending surface IO will be issued to the backend 3D API and
+     * if the surface has MSAA it will be resolved.
+     */
+    void prepareForExternalIO();
+
     bool isStencilBufferMultisampled() const {
         return fRenderTarget->isStencilBufferMultisampled();
     }
     bool isUnifiedMultisampled() const { return fRenderTarget->isUnifiedMultisampled(); }
     bool hasMixedSamples() const { return fRenderTarget->hasMixedSamples(); }
 
     bool mustUseHWAA(const GrPaint& paint) const {
         return paint.isAntiAlias() && fRenderTarget->isUnifiedMultisampled();
     }
 
@@ skipping 100 matching lines @@
 
     sk_sp<SkColorSpace>               fColorSpace;
     SkSurfaceProps                    fSurfaceProps;
     GrAuditTrail*                     fAuditTrail;
 
     // In debug builds we guard against improper thread handling
     SkDEBUGCODE(mutable GrSingleOwner* fSingleOwner;)
 };
 
 #endif