Improve null gpu's memory handling

gm/gmmain.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.
  */
 
 /*
  * Code for the "gm" (Golden Master) rendering comparison tool.
  *
@@ skipping 1240 matching lines @@
     { SkBitmap::kARGB_4444_Config, kRaster_Backend, kDontCare_GLContextType,                  0, kRW_ConfigFlag,    "4444",         true },
 #endif
     { SkBitmap::kRGB_565_Config,   kRaster_Backend, kDontCare_GLContextType,                  0, kRW_ConfigFlag,    "565",          true },
 #if SK_SUPPORT_GPU
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kNative_GLContextType,  0, kRW_ConfigFlag,    "gpu",          true },
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kNative_GLContextType, 16, kRW_ConfigFlag,    "msaa16",       false},
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kNative_GLContextType,  4, kRW_ConfigFlag,    "msaa4",        false},
     /* The gpudebug context does not generate meaningful images, so don't record
      * the images it generates!  We only run it to look for asserts. */
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kDebug_GLContextType,   0, kNone_ConfigFlag,  "gpudebug",     GR_DEBUG},
+    /* The gpunull context does the least amount of work possible and doesn't
+       generate meaninful images, so don't record them!. It can be run to
+       isolate the CPU-side processing expense from the GPU-side.
+      */
+    { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kNull_GLContextType,    0, kNone_ConfigFlag,  "gpunull",      GR_DEBUG},
 #if SK_ANGLE
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kANGLE_GLContextType,   0, kRW_ConfigFlag,    "angle",        true },
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kANGLE_GLContextType,  16, kRW_ConfigFlag,    "anglemsaa16",  true },
 #endif // SK_ANGLE
 #ifdef SK_MESA
     { SkBitmap::kARGB_8888_Config, kGPU_Backend,    GrContextFactory::kMESA_GLContextType,    0, kRW_ConfigFlag,    "mesa",         true },
 #endif // SK_MESA
 #endif // SK_SUPPORT_GPU
 #ifdef SK_SUPPORT_XPS
     /* At present we have no way of comparing XPS files (either natively or by converting to PNG). */
@@ skipping 903 matching lines @@
     if (FLAGS_forceBWtext) {
         canvas->setDrawFilter(SkNEW(BWTextDrawFilter))->unref();
     }
 }
 
 #if !defined(SK_BUILD_FOR_IOS) && !defined(SK_BUILD_FOR_NACL)
 int main(int argc, char * const argv[]) {
     return tool_main(argc, (char**) argv);
 }
 #endif