Have GMs read the GrContext via a setter/getter rather than a global.

gm/image.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 "gm.h"
 #include "SkSurface.h"
 #include "SkCanvas.h"
 #include "SkStream.h"
 #include "SkData.h"
 
 #if SK_SUPPORT_GPU
 #include "GrContext.h"
-
-namespace skiagm {
-extern GrContext* GetGr();
-};
 #endif
 
 static SkData* fileToData(const char path[]) {
     SkFILEStream stream(path);
     if (!stream.isValid()) {
         return SkData::NewEmpty();
     }
     size_t size = stream.getLength();
     void* mem = sk_malloc_throw(size);
     stream.read(mem, size);
@@ skipping 156 matching lines @@
 
         info.fWidth = W;
         info.fHeight = H;
         info.fColorType = SkImage::kPMColor_ColorType;
         info.fAlphaType = SkImage::kPremul_AlphaType;
         SkAutoTUnref<SkSurface> surf0(SkSurface::NewRasterDirect(info, fBuffer, RB));
         SkAutoTUnref<SkSurface> surf1(SkSurface::NewRaster(info));
         SkAutoTUnref<SkSurface> surf2(SkSurface::NewPicture(info.fWidth, info.fHeight));
         SkAutoTUnref<SkSurface> surf3(SkSurface::NewPicture(info.fWidth, info.fHeight));
 #if SK_SUPPORT_GPU
-        GrContext* ctx = skiagm::GetGr();
+        GrContext* ctx = GM::GetGr(canvas);
 
         SkAutoTUnref<SkSurface> surf4(SkSurface::NewRenderTarget(ctx, info, 0));
 #endif
 
         test_surface(canvas, surf0, true);
         canvas->translate(80, 0);
         test_surface(canvas, surf1, true);
         canvas->translate(80, 0);
         test_surface(canvas, surf2, true);
         canvas->translate(80, 0);
@@ skipping 11 matching lines @@
     }
 
 private:
     typedef skiagm::GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static skiagm::GM* MyFactory(void*) { return new ImageGM; }
 static skiagm::GMRegistry reg(MyFactory);