Enable crash dump collection on builders

win_toolchain/get_toolchain_if_necessary.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Downloads and unpacks a toolchain for building on Windows. The contents are
 matched by sha1 which will be updated when the toolchain is updated.
 
 Having a toolchain script in depot_tools means that it's not versioned
 directly with the source code. That is, if the toolchain is upgraded, but
@@ skipping 339 matching lines @@
     return 'Windows8.1-KB2999226-x64.msu'
   else:
     # Some future OS.
     return None
 
 
 def InstallUniversalCRTIfNeeded(abs_target_dir):
   return
 
 
+def EnableCrashDumpCollection():
+  """Tell Windows Error Reporting to record crash dumps so that we can diagnose
+  linker crashes and other toolchain failures. Documented at:
+  https://msdn.microsoft.com/en-us/library/windows/desktop/bb787181.aspx
+  """
+  if sys.platform == 'win32' and os.environ.get('CHROME_HEADLESS') == '1':
+    key_name = r'SOFTWARE\Microsoft\Windows\Windows Error Reporting'
+    try:
+      key = winreg.CreateKey(winreg.HKEY_LOCAL_MACHINE, key_name)
+      # Merely creating LocalDumps is sufficient to enable the defaults.
+      winreg.CreateKey(key, "LocalDumps")
+      # Disable the WER UI, as documented here:
+      # https://msdn.microsoft.com/en-us/library/windows/desktop/bb513638.aspx
+      winreg.SetValueEx(key, "DontShowUI", 0, winreg.REG_DWORD, 1)
+    # Trap OSError instead of WindowsError so pylint will succeed on Linux.
+    # Catching errors is important because some build machines are not elevated
+    # and writing to HKLM requires elevation.
+    except OSError:
+      pass
+
+
 def main():
   parser = optparse.OptionParser(description=sys.modules[__name__].__doc__)
   parser.add_option('--output-json', metavar='FILE',
                     help='write information about toolchain to FILE')
   parser.add_option('--force', action='store_true',
                     help='force script to run on non-Windows hosts')
   options, args = parser.parse_args()
 
   if not (sys.platform.startswith(('cygwin', 'win32')) or options.force):
     return 0
@@ skipping 94 matching lines @@
           'Got wrong hash after pulling a new toolchain. '
           'Wanted \'%s\', got one of \'%s\'.' % (
               desired_hash, ', '.join(current_hashes)))
       return 1
     SaveTimestampsAndHash(target_dir, desired_hash)
 
   if options.output_json:
     shutil.copyfile(os.path.join(target_dir, '..', 'data.json'),
                     options.output_json)
 
+  EnableCrashDumpCollection()
+
   if os.environ.get('GYP_MSVS_VERSION') == '2015':
     InstallUniversalCRTIfNeeded(abs_toolchain_target_dir)
 
   RemoveUnusedToolchains(target_dir)
 
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main())