Make a single GrSingleOwner in GrContext

include/gpu/GrContext.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrContext_DEFINED
 #define GrContext_DEFINED
 
@@ skipping 373 matching lines @@
     // from the sw backend. readSurfacePixels is reentrant in one case - when performing
     // the PM conversions test. To handle this we do the PM conversions test outside
     // of fReadPixelsMutex and use a separate mutex to guard it. When it re-enters
     // readSurfacePixels it will grab fReadPixelsMutex and release it before the outer
     // readSurfacePixels proceeds to grab it.
     // TODO: Stop pretending to make GrContext thread-safe for sw rasterization and provide
     // a mechanism to make a SkPicture safe for multithreaded sw rasterization.
     SkMutex                         fReadPixelsMutex;
     SkMutex                         fTestPMConversionsMutex;
 
     // In debug builds we guard against improper thread handling

[robertphillips, 2016/01/07 16:44:11]

// This guard is passed to the GrDrawingManager and, from there, to all the
GrDrawContexts. 

?

-    SkDEBUGCODE(mutable GrSingleOwner fSingleOwner;)
+    mutable GrSingleOwner fSingleOwner;
 
     struct CleanUpData {
         PFCleanUpFunc fFunc;
         void*         fInfo;
     };
 
     SkTDArray<CleanUpData>          fCleanUpData;
 
     const uint32_t                  fUniqueID;
 
@@ skipping 36 matching lines @@
     /**
      * A callback similar to the above for use by the TextBlobCache
      * TODO move textblob draw calls below context so we can use the call above.
      */
     static void TextBlobCacheOverBudgetCB(void* data);
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif