[fuchsia] Remove stale references to webrunner.

The //fuchsia directory should no longer use "webrunner". Change some
of the remaining references to "web_engine" or "WebEngine".

Bug: 922635
Change-Id: I0fd8beb838c76a0a39b54c4aa78f0d73194ae02a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1579779
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654158}
4 files changed