Add gyp_webrtc script to generate projects.

The reason for this is that http://crrev.com/245412
introduces a dependency of Chrome's src/build/gyp_chromium
to src/tools/find_depot_tools.py, which we don't have
synced in WebRTC (src/tools is very big).

Offline discussions shows that we cannot rely on syncing
individual subdirectories from Chrome in the future, but
maintaining our own gyp_webrtc file will at least buy us
some time for now, so we can roll past that chromium_revision
in WebRTC DEPS.

Overview of differences between gyp_webrtc and gyp_chromium
(and how we previously used gyp_chromium):
* No .gyp file needs to be passed (defaults to all.gyp)
* CHROMIUM_GYP_FILE is ignored (i.e. cannot be used to
  specify an alternate .gyp file to process)
* Ninja is used by default on all platforms unless GYP_GENERATORS
  is set.
* Gyp syntax check is always on
* Gyp circular dependency check is always on
* No support for automatic toolchain detection on Windows.
* --depth argument is no longer needed since calculated by
  the script.
* Support for a webrtc.gyp_env file sitting next to the
  .gclient file in the top dir of checkout, which can be
  used to override Gyp variables similar to chromium.gyp_env.
* SKIP_WEBRTC_GYP_ENV can be set to skip reading webrtc.gyp_env.

BUG=2863
TEST=Ran and verified behavior on Linux with:
gclient runhooks
webrtc/build/gyp_webrtc
webrtc/build/gyp_webrtc -Dextra_gyp_flag=0
. build/android/envsetup.sh && gclient runhooks
SKIP_WEBRTC_GYP_ENV=1 webrtc/build/gyp_webrtc
GYP_GENERATORS=make webrtc/build/gyp_webrtc

The patch also passes runhooks and compile step on all trybots.

R=andrew@webrtc.org, fischman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/7759004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5467 4adac7df-926f-26a2-2b94-8c16560cd09d

DEPS

@@ -281,8 +281,7 @@ hooks = [
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",
-    "action": ["python", Var("root_dir") + "/build/gyp_chromium",
-               "--depth=" + Var("root_dir"), Var("root_dir") + "/all.gyp",
+    "action": ["python", Var("root_dir") + "/webrtc/build/gyp_webrtc",
                Var("extra_gyp_flag")],
   },
 ]

webrtc/build/gyp_webrtc

@@ -0,0 +1,80 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+# This script is used to run GYP for WebRTC. It contains selected parts of the
+# main function from the src/build/gyp_chromium file.
+
+import glob
+import os
+import shlex
+import sys
+
+script_dir = os.path.dirname(os.path.realpath(__file__))
+checkout_root = os.path.abspath(os.path.join(script_dir, os.pardir, os.pardir))
+chrome_build_dir = os.path.join(checkout_root, 'build')
+
+sys.path.insert(0, chrome_build_dir)
+import gyp_chromium
+import gyp_helper
+
+sys.path.insert(0, os.path.join(checkout_root, 'tools', 'gyp', 'pylib'))
+import gyp
+
+
+if __name__ == '__main__':
+  args = sys.argv[1:]
+
+  if int(os.environ.get('GYP_CHROMIUM_NO_ACTION', 0)):
+    print 'Skipping gyp_webrtc due to GYP_CHROMIUM_NO_ACTION env var.'
+    sys.exit(0)
+
+  if 'SKIP_WEBRTC_GYP_ENV' not in os.environ:
+    # Update the environment based on webrtc.gyp_env
+    gyp_env_path = os.path.join(os.path.dirname(checkout_root),
+                                'webrtc.gyp_env')
+    gyp_helper.apply_gyp_environment_from_file(gyp_env_path)
+
+  # This could give false positives since it doesn't actually do real option
+  # parsing.  Oh well.
+  gyp_file_specified = False
+  for arg in args:
+    if arg.endswith('.gyp'):
+      gyp_file_specified = True
+      break
+
+  # If we didn't get a file, assume 'all.gyp' in the root of the checkout.
+  if not gyp_file_specified:
+    args.append(os.path.join(checkout_root, 'all.gyp'))
+
+  # There shouldn't be a circular dependency relationship between .gyp files,
+  args.append('--no-circular-check')
+
+  # Default to ninja unless GYP_GENERATORS is set.
+  if not os.environ.get('GYP_GENERATORS'):
+    os.environ['GYP_GENERATORS'] = 'ninja'
+
+  # Enforce gyp syntax checking. This adds about 20% execution time.
+  args.append('--check')
+
+  supplemental_includes = gyp_chromium.GetSupplementalFiles()
+  if not gyp_chromium.RunGN(supplemental_includes):
+    sys.exit(1)
+  args.extend(['-I' + i for i in
+               gyp_chromium.additional_include_files(supplemental_includes,
+                                                     args)])
+
+  # Set the gyp depth variable to the root of the checkout.
+  args.append('--depth=' + os.path.relpath(checkout_root))
+
+  print 'Updating projects from gyp files...'
+  sys.stdout.flush()
+
+  # Off we go...
+  sys.exit(gyp.main(args))

webrtc/build/gyp_webrtc.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python
+#
+# Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
+#
+# Use of this source code is governed by a BSD-style license
+# that can be found in the LICENSE file in the root of the source
+# tree. An additional intellectual property rights grant can be found
+# in the file PATENTS.  All contributing project authors may
+# be found in the AUTHORS file in the root of the source tree.
+
+# This file is (possibly, depending on python version) imported by
+# gyp_webrtc when GYP_PARALLEL=1 and it creates sub-processes
+# through the multiprocessing library.
+
+# Importing in Python 2.6 (fixed in 2.7) on Windows doesn't search for
+# imports that don't end in .py (and aren't directories with an
+# __init__.py). This wrapper makes "import gyp_webrtc" work with
+# those old versions and makes it possible to execute gyp_webrtc.py
+# directly on Windows where the extension is useful.
+
+import os
+
+path = os.path.abspath(os.path.split(__file__)[0])
+execfile(os.path.join(path, 'gyp_webrtc'))