Download GN in the gclient hooks.

Recently git cl format has started requiring GN and would fail when run
in the ANGLE standalone repository because the binary was not present.

BUG=

Change-Id: I0482db6fd6a868dc02ef6e395e6ff4817623c291
Reviewed-on: https://chromium-review.googlesource.com/326420
Reviewed-by: Jamie Madill <[email protected]>
Reviewed-by: Geoff Lang <[email protected]>
Commit-Queue: Corentin Wallez <[email protected]>

Author: Kangz

Diff for: DEPS

@@ -66,6 +66,40 @@ hooks = [
                 '-s', 'buildtools/linux64/clang-format.sha1',
     ],
   },
+  # Pull GN binaries using checked-in hashes.
+  {
+    'name': 'gn_win',
+    'pattern': '.',
+    'action': [ 'download_from_google_storage',
+                '--no_resume',
+                '--platform=win32',
+                '--no_auth',
+                '--bucket', 'chromium-gn',
+                '-s', 'buildtools/win/gn.exe.sha1',
+    ],
+  },
+  {
+    'name': 'gn_mac',
+    'pattern': '.',
+    'action': [ 'download_from_google_storage',
+                '--no_resume',
+                '--platform=darwin',
+                '--no_auth',
+                '--bucket', 'chromium-gn',
+                '-s', 'buildtools/mac/gn.sha1',
+    ],
+  },
+  {
+    'name': 'gn_linux64',
+    'pattern': '.',
+    'action': [ 'download_from_google_storage',
+                '--no_resume',
+                '--platform=linux*',
+                '--no_auth',
+                '--bucket', 'chromium-gn',
+                '-s', 'buildtools/linux64/gn.sha1',
+    ],
+  },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     "pattern": ".",