Add watchlist entry for libvpx.

WATCHLISTS

Index: WATCHLISTS
diff --git a/WATCHLISTS b/WATCHLISTS
index 96d2e82ba1c40c5717ac59f3728be145a441ed0c..a59903fb5a56084c129781a3ba8b63f81dece0b6 100644
--- a/WATCHLISTS
+++ b/WATCHLISTS
@@ -357,6 +357,9 @@
     'ipc': {
       'filepath': 'ipc/ipc',
     },
+    'libvpx': {
+      'filepath': 'third_party/libvpx'
+    },
     'libwebp': {
       'filepath': 'third_party/libwebp'
     },
@@ -810,6 +813,8 @@
                 'jfweitz+watch@chromium.org', 'skanuj+watch@chromium.org',
                 'donnd+watch@chromium.org'],
     'ipc': ['jam@chromium.org', 'darin-cc@chromium.org'],
+    'libvpx': ['tomfinegan@chromium.org', 'jzern@chromium.org',
+               'fgalligan@chromium.org', 'johannkoenig@chromium.org'],
     'libwebp': ['urvang@google.com', 'jzern@chromium.org',
                 'skal@google.com', 'vikasa@google.com'],
     'linux_fonts': ['derat+watch@chromium.org'],