guarded change to SkImageGenerator to make getInfo() const

tests/SurfaceTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkImageEncoder.h"
@@ skipping 49 matching lines @@
 enum ImageType {
     kRasterCopy_ImageType,
     kRasterData_ImageType,
     kGpu_ImageType,
     kCodec_ImageType,
 };
 
 #include "SkImageGenerator.h"
 
 class EmptyGenerator : public SkImageGenerator {
-protected:
-    bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
-        *info = SkImageInfo::Make(0, 0, kN32_SkColorType, kPremul_SkAlphaType);
-        return true;
-    }
+public:
+    EmptyGenerator() : SkImageGenerator(SkImageInfo::MakeN32Premul(0, 0)) {}
 };
 
 static void test_empty_image(skiatest::Reporter* reporter) {
     const SkImageInfo info = SkImageInfo::Make(0, 0, kN32_SkColorType, kPremul_SkAlphaType);
     
     REPORTER_ASSERT(reporter, NULL == SkImage::NewRasterCopy(info, NULL, 0));
     REPORTER_ASSERT(reporter, NULL == SkImage::NewRasterData(info, NULL, 0));
     REPORTER_ASSERT(reporter, NULL == SkImage::NewFromGenerator(SkNEW(EmptyGenerator)));
 }
 
@@ skipping 485 matching lines @@
                 TestSurfaceNoCanvas(reporter, kGpuScratch_SurfaceType, context, SkSurface::kRetain_ContentChangeMode);
                 TestGetTexture(reporter, kGpu_SurfaceType, context);
                 TestGetTexture(reporter, kGpuScratch_SurfaceType, context);
                 test_empty_surface(reporter, context);
                 test_surface_budget(reporter, context);
             }
         }
     }
 #endif
 }