Revert of Remove gyp-win-tool.

build/toolchain/win/setup_toolchain.py

Index: build/toolchain/win/setup_toolchain.py
diff --git a/build/toolchain/win/setup_toolchain.py b/build/toolchain/win/setup_toolchain.py
index fbc201ec1abd3109d981df8446851abaf3d548f3..0d0975dfe3a6444719fea252becfd87b37448069 100644
--- a/build/toolchain/win/setup_toolchain.py
+++ b/build/toolchain/win/setup_toolchain.py
@@ -46,9 +46,10 @@
       if re.match(envvar + '=', line.lower()):
         var, setting = line.split('=', 1)
         if envvar == 'path':
-          # Our own rules and actions in Chromium rely on python being in the
-          # path. Add the path to this python here so that if it's not in the
-          # path when ninja is run later, python will still be found.
+          # Our own rules (for running gyp-win-tool) and other actions in
+          # Chromium rely on python being in the path. Add the path to this
+          # python here so that if it's not in the path when ninja is run
+          # later, python will still be found.
           setting = os.path.dirname(sys.executable) + os.pathsep + setting
         env[var.upper()] = setting
         break
@@ -146,16 +147,45 @@
   return block
 
 
+def _CopyTool(source_path):
+  """Copies the given tool to the current directory, including a warning not
+  to edit it."""
+  with open(source_path) as source_file:
+    tool_source = source_file.readlines()
+
+  # Add header and write it out to the current directory (which should be the
+  # root build dir). Don't write the file if a matching file already exists
+  # because that causes a cascade of unnecessary rebuilds.
+  match = False
+  contents = ''.join([tool_source[0],
+                      '# Generated by setup_toolchain.py do not edit.\n']
+                     + tool_source[1:])
+  out_path = 'gyp-win-tool'
+  try:
+    with open(out_path, 'rb') as read_tool_file:
+      existing_contents = read_tool_file.read()
+    if existing_contents == contents:
+      match = True
+  except:
+    pass
+  if not match:
+    with open(out_path, 'wb') as write_tool_file:
+      write_tool_file.write(contents)
+
+
 def main():
-  if len(sys.argv) != 6:
+  if len(sys.argv) != 7:
     print('Usage setup_toolchain.py '
-          '<visual studio path> <win sdk path> '
+          '<visual studio path> <win tool path> <win sdk path> '
           '<runtime dirs> <target_cpu> <include prefix>')
     sys.exit(2)
-  win_sdk_path = sys.argv[2]
-  runtime_dirs = sys.argv[3]
-  target_cpu = sys.argv[4]
-  include_prefix = sys.argv[5]
+  tool_source = sys.argv[2]
+  win_sdk_path = sys.argv[3]
+  runtime_dirs = sys.argv[4]
+  target_cpu = sys.argv[5]
+  include_prefix = sys.argv[6]
+
+  _CopyTool(tool_source)
 
   cpus = ('x86', 'x64')
   assert target_cpu in cpus