Roll DevTools Frontend from efb5e1e501fe to 2c6b51469688 (2 revisions)

https://chromium.googlesource.com/devtools/devtools-frontend.git/+log/efb5e1e501fe..2c6b51469688

2020-06-15 zhin@chromium.org Add ChainExpression to ESTreeWalker
2020-06-15 pfaffe@chromium.org [wasm debugging] Fix lookup of llvm-lit

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/devtools-frontend-chromium
Please CC devtools-waterfall-sheriff-onduty@grotations.appspotmail.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

Bug: chromium:1083214
Tbr: devtools-waterfall-sheriff-onduty@grotations.appspotmail.com
Change-Id: Ibd9fed4c0ef6472926cd610422d7fbb2ae0a7446
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2246779Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#778399}

DEPS

@@ -253,7 +253,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling devtools-frontend
   # and whatever else without interference from each other.
-  'devtools_frontend_revision': 'efb5e1e501fe83dc54eaa03a3d09a06e852d9ab8',
+  'devtools_frontend_revision': '2c6b51469688e23f7d63d1791d17197c83223cdc',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling libprotobuf-mutator
   # and whatever else without interference from each other.