Add hook to remove stale pyc files from catapult project

DEPS

 # This file is used to manage the dependencies of the Chromium src repo. It is
 # used by gclient to determine what version of each dependency to check out, and
 # where.
 #
 # For more information, please refer to the official documentation:
 #   https://sites.google.com/a/chromium.org/dev/developers/how-tos/get-the-code
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 #
@@ skipping 819 matching lines @@
     'name': 'remove_stale_pyc_files',
     'pattern': '.',
     'action': [
         'python',
         'src/tools/remove_stale_pyc_files.py',
         'src/android_webview/tools',
         'src/gpu/gles2_conform_support',
         'src/infra',
         'src/ppapi',
         'src/printing',
+        'src/third_party/catapult',
         'src/third_party/closure_compiler/build',
         'src/tools',
     ],
   },
   {
     # A change to a .gyp, .gypi, or to GYP itself should run the generator.
     'name': 'gyp',
     'pattern': '.',
     'action': ['python', 'src/build/gyp_chromium'],
   },
 ]