Roll src/third_party/devtools-frontend/src 1e430429c148..254ce3f8dfb0 (2 commits)

https://chromium.googlesource.com/devtools/devtools-frontend.git/+log/1e430429c148..254ce3f8dfb0

git log 1e430429c148..254ce3f8dfb0 --date=short --first-parent --format='%ad %ae %s'
2019-12-20 comoody@microsoft.com Add undefined check in contentAsDataUrl to prevent unhandled exceptions
2019-12-20 tmathmeyer@chromium.org Redesign Media properties view

Created with:
  gclient setdep -r src/third_party/devtools-frontend/src@254ce3f8dfb0

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/+/master/autoroll/README.md

Bug: chromium:794255
Tbr: devtools-waterfall-sheriff-onduty@grotations.appspotmail.com
Change-Id: I048c9e34393e50ace6600a892333f2268b3d27b6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1979419Reviewed-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@{#727000}

DEPS

@@ -246,7 +246,7 @@ 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': '1e430429c148226c7fc30079c388ee345b0c3dbb',
+  'devtools_frontend_revision': '254ce3f8dfb02a2a3223718d8d080f2f388096ad',
   # 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.