Add `SkIRect bounds()` convenience method to SkImageInfo and SkBitmap.

tests/ImageNewShaderTest.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkTypes.h"
 #if SK_SUPPORT_GPU
 #include "GrContextFactory.h"
@@ skipping 38 matching lines @@
             SkShader::kRepeat_TileMode,
             SkShader::kRepeat_TileMode));
 
     SkPaint paint;
     paint.setShader(sourceShader);
 
     SkCanvas* destinationCanvas = destinationSurface->getCanvas();
     destinationCanvas->clear(SK_ColorTRANSPARENT);
     destinationCanvas->drawPaint(paint);
 
-    SkIRect rect = SkIRect::MakeWH(info.width(), info.height());
+    SkIRect rect = info.bounds();
 
     SkBitmap bmOrig;
     sourceSurface->getCanvas()->readPixels(rect, &bmOrig);
 
 
     SkBitmap bm;
     destinationCanvas->readPixels(rect, &bm);
 
     testBitmapEquality(reporter, bmOrig, bm);
 
@@ skipping 88 matching lines @@
 
         //  GPU -> RASTER
         gpuToRaster(reporter, context);
 
         //  RASTER -> GPU
         rasterToGpu(reporter, context);
     }
 }
 
 #endif