Pull in Chromium dependencies from HEAD

GITDEPS

 # Copyright 2015 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
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 # This file is read by gitdeps.py to allow loading subsections of git repos
 # through sparse checkouts.
 
 vars = {
-  "chrome_revision": "a691a7278a6f58da832b8818d2d00afa0687cd0d",
+  "chrome_revision": "HEAD",
   "gyp_revision": "bac4680ec9a5c55ab692490b6732999648ecf1e9",
   "chrome_base_git": "https://chromium.googlesource.com/",
 }
 
 deps = {
   "":(
     Var("chrome_base_git") + "chromium/src",
     [
       # Chrome base and other top-level dependencies.
       "base",
       "build",
       "testing",
       "tools",
 
       # third_party dependencies.
       "third_party/protobuf",
     ],
     Var("chrome_revision")
   ),
   "tools/gyp":
     (Var("chrome_base_git") + "external/gyp/",
     [],
     Var("gyp_revision")),
 }