Adds support for webrtc::test::ResourcePath on iOS

BUG=webrtc:4752
R=tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1178843002.

Cr-Original-Commit-Position: refs/heads/master@{#9445}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 1d34fe979c52e5826c5c8162759b0167b2607836
14 files changed