Add GN bootstrap step to continuous integration

tools/gn/bootstrap/bootstrap.py

Index: tools/gn/bootstrap/bootstrap.py
diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index 373883f8e348e1dd536d4b7f410776d6f25fa02b..2dc2a03e769238d889502ca1c2d5fb487a1f5407 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -11,6 +11,7 @@ it with its own BUILD.gn to the final destination.
 
 import contextlib
 import errno
+import json
 import logging
 import optparse
 import os
@@ -56,8 +57,14 @@ def main(argv):
                     help='place output in PATH', metavar='PATH')
   parser.add_option('-s', '--no-rebuild', action='store_true',
                     help='Do not rebuild GN with GN.')
+  parser.add_option('--temp-build-dir', action='store_true',
+                    help='Build GN in temporary directory')
+  parser.add_option('--use-bundled-clang', action='store_true',
+                    help='Use bundled clang compiler (e.g. when host toolchain '
+                         'is too old to support C++11)')
   parser.add_option('-v', '--verbose', action='store_true',
                     help='Log more details')
+  parser.add_option('--json')
   options, args = parser.parse_args(argv)
 
   if args:
@@ -69,29 +76,38 @@ def main(argv):
     build_rel = os.path.join('out', 'Debug')
   else:
     build_rel = os.path.join('out', 'Release')
-  build_root = os.path.join(SRC_ROOT, build_rel)
+
+  failures = []
 
   try:
     with scoped_tempdir() as tempdir:
       print 'Building gn manually in a temporary directory for bootstrapping...'
       build_gn_with_ninja_manually(tempdir, options)
       temp_gn = os.path.join(tempdir, 'gn')
+      if options.temp_build_dir:
+        build_root = os.path.join(tempdir, 'build_root')
+      else:
+        build_root = os.path.join(SRC_ROOT, build_rel)
       out_gn = os.path.join(build_root, 'gn')
 
       if options.no_rebuild:
         mkdir_p(build_root)
         shutil.copy2(temp_gn, out_gn)
       else:
-        print 'Building gn using itself to %s...' % build_rel
-        build_gn_with_gn(temp_gn, build_rel, options)
+        print 'Building gn using itself to %s...' % build_root
+        build_gn_with_gn(temp_gn, build_root, options)
 
       if options.output:
         # Preserve the executable permission bit.
         shutil.copy2(out_gn, options.output)
   except subprocess.CalledProcessError as e:
     print >> sys.stderr, str(e)
-    return 1
-  return 0
+    failures.append(str(e))
+
+  if options.json:
+    with open(options.json, 'w') as f:
+      json.dump(failures, f)
+  return 1 if failures else 0
 
 
 def build_gn_with_ninja_manually(tempdir, options):
@@ -103,8 +119,15 @@ def build_gn_with_ninja_manually(tempdir, options):
   check_call(cmd)
 
 def write_ninja(path, options):
-  cc = os.environ.get('CC', '')
-  cxx = os.environ.get('CXX', '')
+  default_cc = ''
+  default_cxx = ''
+  if options.use_bundled_clang:
+    clang_dir = os.path.join(
+        SRC_ROOT, 'third_party', 'llvm-build', 'Release+Asserts', 'bin')
+    default_cc = os.path.join(clang_dir, 'clang')
+    default_cxx = os.path.join(clang_dir, 'clang++')
+  cc = os.environ.get('CC', default_cc)
+  cxx = os.environ.get('CXX', default_cxx)
   cflags = os.environ.get('CFLAGS', '').split()
   cflags_cc = os.environ.get('CXXFLAGS', '').split()
   ld = os.environ.get('LD', cxx)
@@ -227,10 +250,13 @@ def write_ninja(path, options):
       'base/time/time.cc',
       'base/timer/elapsed_timer.cc',
       'base/timer/timer.cc',
+      'base/trace_event/category_filter.cc',
+      'base/trace_event/trace_config.cc',
       'base/trace_event/trace_event_impl.cc',
       'base/trace_event/trace_event_impl_constants.cc',
       'base/trace_event/trace_event_memory.cc',
       'base/trace_event/trace_event_synthetic_delay.cc',
+      'base/trace_event/trace_options.cc',
       'base/tracked_objects.cc',
       'base/tracking_info.cc',
       'base/values.cc',