Turn off buffer mapping in Chromium

src/gpu/gl/GrGLCaps.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "GrGLCaps.h"
 
@@ skipping 359 matching lines @@
             fMapBufferType = kMapBufferRange_MapBufferType;
         } else if (ctxInfo.hasExtension("GL_OES_mapbuffer")) {
             fMapBufferFlags = kCanMap_MapFlag;
             fMapBufferType = kMapBuffer_MapBufferType;
         }
     }
 
     // On many GPUs, map memory is very expensive, so we effectively disable it here by setting the
     // threshold to the maximum unless the client gives us a hint that map memory is cheap.
     if (fGeometryBufferMapThreshold < 0) {
+        // We think mapping on Chromium will be cheaper once we know ahead of time how much space
+        // we will use for all GrBatchs. Right now we might wind up mapping a large buffer and using
+        // a small subset.
+#if 0
         fGeometryBufferMapThreshold = kChromium_GrGLDriver == ctxInfo.driver() ? 0 : SK_MaxS32;
+#else
+        fGeometryBufferMapThreshold = SK_MaxS32;
+#endif
     }
 
     if (kGL_GrGLStandard == standard) {
         SkASSERT(ctxInfo.version() >= GR_GL_VER(2,0) ||
                  ctxInfo.hasExtension("GL_ARB_texture_non_power_of_two"));
         fNPOTTextureTileSupport = true;
         fMipMapSupport = true;
     } else {
         // Unextended ES2 supports NPOT textures with clamp_to_edge and non-mip filters only
         // ES3 has no limitations.
@@ skipping 767 matching lines @@
         for (int p = 0; p < kGrSLPrecisionCount; ++p) {
             glslCaps->fFloatPrecisions[kGeometry_GrShaderType][p] = 
                                                glslCaps->fFloatPrecisions[kVertex_GrShaderType][p];
         }
     }
 }