Beginning work on GN build

DEPS

Index: DEPS
diff --git a/DEPS b/DEPS
index 138d463eda9b98c9c185537488cd34700379c24b..9236cf037f8d103cc2f849fccb567a5ef197ebf3 100644
--- a/DEPS
+++ b/DEPS
@@ -38,6 +38,7 @@ vars = {
   "bazel_worker_tag": "@v0.1.0",
   "boolean_selector_tag" : "@1.0.0",
   "boringssl_rev" : "@daeafc22c66ad48f6b32fc8d3362eb9ba31b774e",
+  'buildtools_revision': '@06e80a0e17319868d4a9b13f9bb6a248dc8d8b20',
   "charcode_tag": "@1.1.0",
   "chrome_rev" : "@19997",
   "cli_util_tag" : "@0.0.1+2",
@@ -109,10 +110,14 @@ vars = {
   "when_tag": "@0.2.0+2",
   "which_tag": "@0.1.3+1",
   "yaml_tag": "@2.1.5",
-  "zlib_rev": "@c3d0a6190f2f8c924a05ab6cc97b8f975bddd33f",
+  "zlib_rev": "@4576304a4b9835aa8646c9735b079e1d96858633",
 }
 
 deps = {
+  Var("dart_root") + "/buildtools":
+      Var('chromium_git') + '/chromium/buildtools.git' +
+      Var('buildtools_revision'),
+
   # Stuff needed for GYP to run.
   Var("dart_root") + "/third_party/gyp":
       Var('chromium_git') + '/external/gyp.git' + Var("gyp_rev"),
@@ -321,6 +326,83 @@ deps_os = {
 # TODO(iposva): Move the necessary tools so that hooks can be run
 # without the runtime being available.
 hooks = [
+  # Pull GN binaries. This needs to be before running GYP below.
+  {
+    'name': 'gn_linux64',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--quiet',
+      '--platform=linux*',
+      '--bucket',
+      'chromium-gn',
+      '-s',
+      Var('dart_root') + '/buildtools/linux64/gn.sha1',
+    ],
+  },
+  {
+    'name': 'gn_mac',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--quiet',
+      '--platform=darwin',
+      '--bucket',
+      'chromium-gn',
+      '-s',
+      Var('dart_root') + '/buildtools/mac/gn.sha1',
+    ],
+  },
+  {
+    'name': 'gn_win',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--quiet',
+      '--platform=win*',
+      '--bucket',
+      'chromium-gn',
+      '-s',
+      Var('dart_root') + '/buildtools/win/gn.exe.sha1',
+    ],
+  },
+  # Pull clang-format binaries using checked-in hashes.
+  {
+    'name': 'clang_format_linux',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--quiet',
+      '--platform=linux*',
+      '--bucket',
+      'chromium-clang-format',
+      '-s',
+      Var('dart_root') + '/buildtools/linux64/clang-format.sha1',
+    ],
+  },
+  {
+    'name': 'clang_format_mac',
+    'pattern': '.',
+    'action': [
+      'download_from_google_storage',
+      '--no_auth',
+      '--no_resume',
+      '--quiet',
+      '--platform=darwin',
+      '--bucket',
+      'chromium-clang-format',
+      '-s',
+      Var('dart_root') + '/buildtools/mac/clang-format.sha1',
+    ],
+  },
   {
     'name': 'd8_testing_binaries',
     'pattern': '.',