Pull Chromium dependencies to Pipa checkout via DEPS and GITDEPS.

DEPS

+# Copyright 2014 Google Inc. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+vars = {
+  # Name of the directory to which the repository is pulled in.
+  "root": "src",
+  # This is expected to be Python 2.7 from depot_tools.
+  "python_path": "python",
+
+  "chromium_git": "https://chromium.googlesource.com",
+  "buildtools_revision": "a7cc7a3e21a061975b33dcdcd81a9716ba614c3c",
+}
+
+deps = {
+  Var("root") + "/buildtools":
+    Var('chromium_git') + '/chromium/buildtools.git' + '@' +  Var('buildtools_revision'),
+}
+
+include_rules = [
+]
+
+hooks = [
+  {
+    "name": "run_gitdeps",
+    "pattern": ".",
+    "action": [Var("python_path"),
+               Var("root") + "/pipa/build/gitdeps.py",
+               Var("root") + "/GITDEPS",
+               "--output-dir=" + Var("root"),
+               "--cache-dir", Var("root") + "/.gitdeps-cache"],
+  },
+  # Pull GN binaries. This needs to be before running GN below.
+  {
+    "name": "gn_win",
+    "pattern": ".",
+    "action": [ "download_from_google_storage",
+                "--no_resume",
+                "--platform=win32",
+                "--no_auth",
+                "--bucket", "chromium-gn",
+                "-s", Var("root") + "/buildtools/win/gn.exe.sha1",
+    ],
+  },
+  {
+    # Update the Windows toolchain if necessary.
+    "name": "win_toolchain",
+    "pattern": ".",
+    "action": [Var("python_path"),
+               Var("root") + "/build/vs_toolchain.py",
+               "update",
+    ],
+  },
+  # TODO(veranika): run GN here.
+  {
+    "name": "download_clang_format",
+    "pattern": ".",
+    "action": ["download_from_google_storage",
+               "--no_resume",
+               "--platform=win32",
+               "--no_auth",
+               "--bucket", "chromium-clang-format",
+               "-s", Var("root") + "/buildtools/win/clang-format.exe.sha1",
+    ],
+  },
+]