Reland "Add runhooks to download PGO profiles and allow query profile path"

This is a reland of 5f5008fc7536c6f18b6099cb63675882a7b896e9

Original change's description:
> Add runhooks to download PGO profiles and allow query profile path
>
> This CL:
> 1. Adds gclient runhooks to download PGO profiles.
> 2. Allows the build system to query the path to the current profile.
>
> Bug: 1071576
> Change-Id: I6b8954f81b61ef7362f28ca2bf585abd84e1a799
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2165448
> Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#763123}

TBR=thakis@chromium.org

Bug: 1071576
Change-Id: Ib5ccfc60d12fa3d07c344691c81cc63ff3efe642
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2171523
Reviewed-by: Yuke Liao <liaoyuke@chromium.org>
Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Yuke Liao <liaoyuke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#763663}

diff --git a/tools/update_pgo_profiles.py b/tools/update_pgo_profiles.py
new file mode 100755
index 0000000..775604a
--- /dev/null
+++ b/tools/update_pgo_profiles.py

@@ -0,0 +1,139 @@
+#!/usr/bin/env python
+# Copyright 2020 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 pgo profiles for optimizing official Chrome.
+
+This script has the following responsibilities:
+1. Download a requested profile if necessary.
+2. Return a path to the current profile to feed to the build system.
+3. Removed stale profiles (2 days) to save disk spaces because profiles are
+   large (~1GB) and updated frequently (~4 times a day).
+"""
+
+from __future__ import print_function
+
+import argparse
+import os
+import sys
+import time
+
+_SRC_ROOT = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), os.path.pardir))
+sys.path.append(os.path.join(_SRC_ROOT, 'third_party', 'depot_tools'))
+import download_from_google_storage
+
+sys.path.append(os.path.join(_SRC_ROOT, 'build'))
+import gn_helpers
+
+# Absolute path to the directory that stores pgo related state files, which
+# specifcies which profile to update and use.
+_PGO_DIR = os.path.join(_SRC_ROOT, 'chrome', 'build')
+
+# Absolute path to the directory that stores pgo profiles.
+_PGO_PROFILE_DIR = os.path.join(_PGO_DIR, 'pgo_profiles')
+
+
+def _read_profile_name(target):
+  """Read profile name given a target.
+
+  Args:
+    target(str): The target name, such as win32, mac.
+
+  Returns:
+    Name of the profile to update and use, such as:
+    chrome-win32-master-67ad3c89d2017131cc9ce664a1580315517550d1.profdata.
+  """
+  state_file = os.path.join(_PGO_DIR, '%s.pgo.txt' % target)
+  with open(state_file, 'r') as f:
+    profile_name = f.read().strip()
+
+  return profile_name
+
+
+def _remove_unused_profiles(current_profile_name):
+  """Removes unused profiles, except the current one, to save disk space."""
+  days = 2
+  expiration_duration = 60 * 60 * 24 * days
+  for f in os.listdir(_PGO_PROFILE_DIR):
+    if f == current_profile_name:
+      continue
+
+    p = os.path.join(_PGO_PROFILE_DIR, f)
+    age = time.time() - os.path.getmtime(p)
+    if age > expiration_duration:
+      print('Removing profile %s as it hasn\'t been used in the past %d days' %
+            (p, days))
+      os.remove(p)
+
+
+def _update(args):
+  """Update profile if necessary according to the state file.
+
+  Args:
+    args(dict): A dict of cmd arguments, such as target and gs_url_base.
+
+  Raises:
+    RuntimeError: If failed to download profiles from gcs.
+  """
+  profile_name = _read_profile_name(args.target)
+  profile_path = os.path.join(_PGO_PROFILE_DIR, profile_name)
+  if os.path.isfile(profile_path):
+    os.utime(profile_path, None)
+    return
+
+  gsutil = download_from_google_storage.Gsutil(
+      download_from_google_storage.GSUTIL_DEFAULT_PATH)
+  gs_path = 'gs://' + args.gs_url_base.strip('/') + '/' + profile_name
+  code = gsutil.call('cp', gs_path, profile_path)
+  if code != 0:
+    raise RuntimeError('gsutil failed to download "%s"' % gs_path)
+
+  _remove_unused_profiles(profile_name)
+
+
+def _get_profile_path(args):
+  """Returns an absolute path to the current profile.
+
+  Args:
+    args(dict): A dict of cmd arguments, such as target and gs_url_base.
+
+  Raises:
+    RuntimeError: If the current profile is missing.
+  """
+  profile_path = os.path.join(_PGO_PROFILE_DIR, _read_profile_name(args.target))
+  if not os.path.isfile(profile_path):
+    raise RuntimeError('requested profile "%s" doesn\'t exist, please run '
+                       '"gclient runhooks" to download it')
+
+  os.utime(profile_path, None)
+  profile_path.rstrip(os.sep)
+  print(gn_helpers.ToGNString(profile_path))
+
+
+def main():
+  parser = argparse.ArgumentParser(
+      description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
+  parser.add_argument(
+      '--target',
+      required=True,
+      choices=['win32', 'win64', 'mac'],
+      help='Identifier of a specific target platform + architecture.')
+  subparsers = parser.add_subparsers()
+
+  parser_update = subparsers.add_parser('update')
+  parser_update.add_argument(
+      '--gs-url-base',
+      required=True,
+      help='The base GS URL to search for the profile.')
+  parser_update.set_defaults(func=_update)
+
+  parser_get_profile_path = subparsers.add_parser('get_profile_path')
+  parser_get_profile_path.set_defaults(func=_get_profile_path)
+
+  args = parser.parse_args()
+  return args.func(args)
+
+
+if __name__ == '__main__':
+  sys.exit(main())