Add landmine support

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',
   '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': '941118827f5240dedb40082cffb1ead6c6d621cc',
@@ skipping 17 matching lines @@
     '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'],
   },
   {
+    # This clobbers when necessary (based on get_landmines.py). It should be
+    # an early hook but it will need to be run after syncing Chromium and
+    # setting up the links, so the script actually exists.
+    'name': 'landmines',
+    'pattern': '.',
+    'action': [
+        'python',
+        Var('root_dir') + '/build/landmines.py',
+        '--landmine-scripts',
+        Var('root_dir') + '/tools/get_landmines.py',
+        '--src-dir',
+        Var('root_dir'),
+    ],
+  },
+  {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'pattern': '.',
     'action': ['python', Var('root_dir') + '/gyp_libyuv'],
   },
 ]