Fix flakiness of ExtensionBrowserTest

the extension to be loaded, so remove RunLoop::RunUntilIdle
which causes the flaky tests.

ChromeTestExtensionLoader: :LoadExtension is already waiting for
Change-Id: I7c7727617e93b2152e84ec32532ab084b889c745
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1743242
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685199}
2 files changed