DO NOT MERGE:backport test imrpovements from newer platform

This change contains the following changes:
I41758a87 some improvements for browser test harness
I7785f66c prevent browser test from launching non-http urls
Id2f49549 throw RuntimeException if failed to stop a timedout site

Change-Id: Ic44f747c5da4328be8fa15b882ce72f56204b142
1 file changed