[Telemetry] Make the display_url for file:// URLs more sane.

This fixes the perf results output for the image_decoding_benchmark.

BUG=163680
TEST=tools/telemetry/run_tests telemetry.page_unittest

Review URL: https://codereview.chromium.org/11446069

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171817 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed