Landmines support to ease clobbering builds

DEPS

 # This file contains dependencies for WebRTC that are not shared with Chromium.
 # If you wish to add a dependency that is present in Chromium's src/DEPS or a
 # directory from the Chromium checkout, you should add it to setup_links.py
 # instead.
 
 vars = {
   'extra_gyp_flag': '-Dextra_gyp_flag=0',
   'chromium_git': 'https://chromium.googlesource.com',
   'chromium_revision': '6919ce3b8c916bb007b77b08bd3ef93f2fe35f74',
 }
@@ skipping 53 matching lines @@
     'action': ['python', '-u', 'src/sync_chromium.py',
                '--target-revision', Var('chromium_revision')],
   },
   {
     # Create links to shared dependencies in Chromium.
     'name': 'setup_links',
     'pattern': '.',
     'action': ['python', 'src/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',
+        'src/build/landmines.py',
+        '--landmine-scripts',
+        'src/webrtc/build/get_landmines.py',
+        '--src-dir',
+        'src',
+    ],
+  },
+  {
      # Pull sanitizer-instrumented third-party libraries if requested via
      # GYP_DEFINES. This could be done as part of sync_chromium.py above
      # but then we would need to run all the Chromium hooks each time,
      # which will slow things down a lot.
      'name': 'instrumented_libraries',
      'pattern': '\\.sha1',
      'action': ['python', 'src/third_party/instrumented_libraries/scripts/download_binaries.py'],
    },
   {
     # Download test resources, i.e. video and audio files from Google Storage.
     'pattern': '.',
     'action': ['download_from_google_storage',
                '--directory',
                '--recursive',
                '--num_threads=10',
                '--no_auth',
                '--bucket', 'chromium-webrtc-resources',
                'src/resources'],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
     'action': ['python', 'src/webrtc/build/gyp_webrtc',
                Var('extra_gyp_flag')],
   },
 ]