Update DevTools DEPS (trusted)

Rolling third_party/depot_tools: https://chromium.googlesource.com/chromium/tools/depot_tools/+log/615f4a2..abc5109

Roll created at https://cr-buildbucket.appspot.com/build/8710400684740656337

Bug: none
Change-Id: I0d8a90e6c2661928fcf3aea38b7699b755c9e72b
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6700256
Bot-Commit: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Devtools Autoroller <devtools-ci-autoroll-builder@chops-service-accounts.iam.gserviceaccount.com>

Author: devtools-ci-autoroll-builder

DEPS

@@ -18,7 +18,7 @@ vars = {
   'buildtools_revision': 'f30f8f10c9d1ad97480dc08eb72f7d9d1bf4cf89',
 
   'depot_tools_url': 'https://chromium.googlesource.com/chromium/tools/depot_tools.git',
-  'depot_tools_revision': '615f4a2f039e861d496c6e58bbff39821361148f',
+  'depot_tools_revision': 'abc51098824678cbce29d7913c4951a857033c49',
 
   'inspector_protocol_url': 'https://chromium.googlesource.com/deps/inspector_protocol',
   'inspector_protocol_revision': '6d1ae0f13aae6ad381ca31b17b88a0f5af29ca94',