Makes GetBuildTime behave identically on all build types.

build/write_build_date_header.py

Index: build/write_build_date_header.py
diff --git a/build/write_build_date_header.py b/build/write_build_date_header.py
new file mode 100755
index 0000000000000000000000000000000000000000..497f845d651d6a74170e9d081e080746dddabb82
--- /dev/null
+++ b/build/write_build_date_header.py
@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+# Copyright (c) 2016 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.
+"""Writes a file that contains a define that approximates the build date.
+
+The build date is set to the most recent first Sunday of a month, in UTC time,
+or to the current date in an official build.
+"""
+
+import argparse
+import calendar
+import datetime
+import sys
+
+
+def GetFirstSundayOfMonth(month, year):
+  """Returns the first sunday of the given month of the given year."""
+  weeks = calendar.Calendar().monthdays2calendar(year, month)
+  # Return the first day in the first week that is a Sunday.
+  return [date_day[0] for date_day in weeks[0] if date_day[1] == 6][0]
+
+
+def GetBuildDate(build_type):
+  """Gets the approximate build date given the specific build type."""
+  gmt_now = datetime.datetime.utcnow()
+  day = gmt_now.day
+  month = gmt_now.month
+  year = gmt_now.year
+  if build_type != 'official':
+    first_sunday = GetFirstSundayOfMonth(month, year)
+    # If our build is after the first Sunday, we've already refreshed our build
+    # cache on a quiet day, so just use that day.
+    # Otherwise, take the first Sunday of the previous month.
+    if day >= first_sunday:
+      day = first_sunday
+    else:
+      month -= 1
+      if month == 0:
+        month = 12
+        year -= 1
+      day = GetFirstSundayOfMonth(month, year)
+  return "{:%b %d %Y}".format(datetime.date(year, month, day))
+
+
+def main():
+  argument_parser = argparse.ArgumentParser()
+  argument_parser.add_argument('output_file', help='The file to write to')
+  argument_parser.add_argument('build_date_override', nargs='?',
+                               help='Optional override for the build date')
+  args = argument_parser.parse_args()
+
+  official_build_date = GetBuildDate('official')
+  default_build_date = GetBuildDate('default')
+  if build_date_override:
+    official_build_date = default_build_date = build_date_override
+
+  with open(args.output_file, 'w') as output_file:

[M-A Ruel, 2016/02/05 19:16:37]

Change to:

- construct the content
- read the file if it existed
- if expected_content != actual_content:
  - write file

this fixes incremental and null builds.

[Zachary Forman, 2016/02/09 00:02:04]

Done

+    output_file.write('// Generated by //build/write_build_date_header.py\n')
+    output_file.write('#ifndef BUILD_DATE\n')
+    output_file.write('#ifdef OFFICIAL_BUILD\n')
+    output_file.write('#define BUILD_DATE \"{}\"\n'.format(official_build_date))
+    output_file.write('#else\n')
+    output_file.write('#define BUILD_DATE \"{}\"\n'.format(default_build_date))
+    output_file.write('#endif // OFFICIAL_BUILD\n')
+    output_file.write('#endif // BUILD_DATE\n')
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())