Add gflags dependency

DEPS

 vars = {
   # Override root_dir in your .gclient's custom_vars to specify a custom root
   # folder name.
-  "root_dir": "libyuv",
-  "extra_gyp_flag": "-Dextra_gyp_flag=0",
+  'root_dir': 'libyuv',
+  'extra_gyp_flag': '-Dextra_gyp_flag=0',
+  'chromium_git': 'https://chromium.googlesource.com',
 
   # Roll the Chromium Git hash to pick up newer versions of all the
   # dependencies and tools linked to in setup_links.py.
   'chromium_revision': 'bb79186c63ff4eff7a2a318a21731005c53f269b',
 }
 
+# NOTE: Prefer revision numbers to tags for svn deps. Use http rather than
+# https; the latter can cause problems for users behind proxies.
+deps = {
+  'src/third_party/gflags/src':
+    Var('chromium_git') + '/external/gflags/src@e7390f9185c75f8d902c05ed7d20bb94eb914d0c', # from svn revision 82
+}
+
+# Define rules for which include paths are allowed in our source.
+include_rules = [ '+gflags' ]
+
 hooks = [
   {
     # Clone chromium and its deps.
-    "name": "sync chromium",
-    "pattern": ".",
-    "action": ["python", "-u", Var("root_dir") + "/sync_chromium.py",
-               "--target-revision", Var("chromium_revision")],
+    'name': 'sync chromium',
+    'pattern': '.',
+    'action': ['python', '-u', Var('root_dir') + '/sync_chromium.py',
+               '--target-revision', Var('chromium_revision')],
   },
   {
     # Create links to shared dependencies in Chromium.
-    "name": "setup_links",
-    "pattern": ".",
-    "action": ["python", Var("root_dir") + "/setup_links.py"],
+    'name': 'setup_links',
+    'pattern': '.',
+    'action': ['python', Var('root_dir') + '/setup_links.py'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
-    "pattern": ".",
-    "action": ["python", Var("root_dir") + "/gyp_libyuv"],
+    'pattern': '.',
+    'action': ['python', Var('root_dir') + '/gyp_libyuv'],
   },
 ]