Pin depot_tools version in DEPS to prevent breakages

Incompatible upstream changes will be detected in Chromium roll
instead of breaking presubmit

find_depot_tools is already aware of this, see
cea92c51ac%5E%21

BUG=None
NOTRY=True

Review-Url: https://codereview.webrtc.org/2986003002
Cr-Commit-Position: refs/heads/master@{#19165}

DEPS

@@ -48,6 +48,8 @@ deps = {
    Var('chromium_git') + '/external/github.com/catapult-project/catapult.git' + '@' + Var('catapult_revision'),
   'src/third_party/colorama/src':
     Var('chromium_git') + '/external/colorama.git' + '@' + '799604a1041e9b3bc5d2789ecbd7e8db2e18e6b8',
+  'src/third_party/depot_tools':
+    Var('chromium_git') + '/chromium/tools/depot_tools.git' + '@' + '6d0d04458d9c345bc7d77681996d89d6e5fc742c',
   'src/third_party/ffmpeg':
     Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + '97ebed67951a157f6add59046024bff5fa20f4ae',
   'src/third_party/googletest/src':
@@ -166,6 +168,17 @@ hooks = [
         'src',
     ],
   },
+  {
+    # Ensure that the DEPS'd "depot_tools" has its self-update capability
+    # disabled.
+    'name': 'disable_depot_tools_selfupdate',
+    'pattern': '.',
+    'action': [
+        'python',
+        'src/third_party/depot_tools/update_depot_tools_toggle.py',
+        '--disable',
+    ],
+  },
   # Android dependencies. Many are downloaded using Google Storage these days.
   # They're copied from https://cs.chromium.org/chromium/src/DEPS for all
   # such dependencies we share with Chromium.