On Windows, fail if there are missing files specified in the project.

gyp_skia

 #!/usr/bin/python
 
 # Copyright 2011 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.
 
 # This script is a wrapper which invokes gyp with the correct --depth argument,
 # and supports the automatic regeneration of build files if all.gyp is
 # changed (Linux-only).
@@ skipping 11 matching lines @@
 
 # Directory within which we can find most of Skia's gyp configuration files.
 gyp_config_dir = os.path.join(script_dir, 'gyp')
 
 # Ensure we import our current gyp source's module, not any version
 # pre-installed in your PYTHONPATH.
 sys.path.insert(0, os.path.join(gyp_source_dir, 'pylib'))
 import gyp
 
 ENVVAR_GYP_GENERATORS = 'GYP_GENERATORS'
+ENVVAR_GYP_GENERATOR_FLAGS = 'GYP_GENERATOR_FLAGS'
 
 
 def additional_include_files(args=[]):
   # Determine the include files specified on the command line.
   # This doesn't cover all the different option formats you can use,
   # but it's mainly intended to avoid duplicating flags on the automatic
   # makefile regeneration which only uses this format.
   specified_includes = set()
   for arg in args:
     if arg.startswith('-I') and len(arg) > 2:
@@ skipping 77 matching lines @@
 
   # Tell gyp to write the build files into output_dir.
   args.extend(['--generator-output', os.path.abspath(get_output_dir())])
 
   # Tell ninja to write its output into the same directory.
   args.extend(['-Goutput_dir=.'])
 
   # By default, we build 'most' instead of 'all' or 'everything'. See skia.gyp.
   args.extend(['-Gdefault_target=most'])
 
+  # Fail if any files specified in the project are missing
+  if sys.platform.startswith('win'):
+    gyp_generator_flags = os.getenv(ENVVAR_GYP_GENERATOR_FLAGS, '')
+    if not 'msvs_error_on_missing_sources' in gyp_generator_flags:
+      os.environ[ENVVAR_GYP_GENERATOR_FLAGS] = (
+          gyp_generator_flags + ' msvs_error_on_missing_sources=1')
+
   print 'Updating projects from gyp files...'
   sys.stdout.flush()
 
   if '--dry-run' in args:
     args.remove('--dry-run')
     print gyp_source_dir, ' '.join(args)
   else:
     # Off we go...
     sys.exit(gyp.main(args))