Make LTCG optional on windows builds.

gyp/common_variables.gypi

 # Copyright 2012 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   # Get ready for the ugly...
   #
   # - We have to nest our variables dictionaries multiple levels deep, so that
   #   this and other gyp files can rely on previously-set variable values in
@@ skipping 196 matching lines @@
     'skia_resource_cache_mb_limit%': '<(skia_resource_cache_mb_limit)',
     'skia_resource_cache_count_limit%': '<(skia_resource_cache_count_limit)',
     'skia_angle%': '<(skia_angle)',
     'skia_poppler_enabled%': '<(skia_poppler_enabled)',
     'skia_arch_width%': '<(skia_arch_width)',
     'skia_arch_type%': '<(skia_arch_type)',
     'skia_chrome_utils%': '<(skia_chrome_utils)',
     'skia_directwrite%': '<(skia_directwrite)',
     'skia_gpu%': '<(skia_gpu)',
     'skia_win_exceptions%': 0,
+    'skia_win_ltcg%': 1,
     'skia_osx_deployment_target%': '<(skia_osx_deployment_target)',
     'skia_profile_enabled%': '<(skia_profile_enabled)',
     'skia_shared_lib%': '<(skia_shared_lib)',
     'skia_opencl%': '<(skia_opencl)',
     'skia_force_distancefield_fonts%': '<(skia_force_distancefield_fonts)',
     'skia_static_initializers%': '<(skia_static_initializers)',
     'ios_sdk_version%': '6.0',
     'skia_win_debuggers_path%': '<(skia_win_debuggers_path)',
     'skia_run_pdfviewer_in_gm%': 0,
     'skia_disable_inlining%': 0,
     'skia_moz2d%': 0,
 
     # These are referenced by our .gypi files that list files (e.g. core.gypi)
     #
     'skia_src_path%': '../src',
     'skia_include_path%': '../include',
   },
 }