[telemetry] Added --results-label option.

Would like to use this on the perf try bot to label the results of performance runs. At the moment, there's no way for a user to distinguish between the Patched/Not Patched result graphs.

BUG=
TEST=

Run: tools/perf/run_measurement -v --browser=release blink_perf third_party/WebKit/PerformanceTests/Layout/floats_50_100.html

Graph results would be labelled "r228994" or whatever your ToT is.


Run: tools/perf/run_measurement -v --browser=release blink_perf third_party/WebKit/PerformanceTests/Layout/floats_50_100.html --result-label=Patch

Graph results would be labelled "Patch", with the previous run called "r228994"

Review URL: https://codereview.chromium.org/26573010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229888 0039d316-1c4b-4281-b951-d872f2087c98
Mojo: Add debug-only checks to Waiter that check that Init() has been called.

(And fix a test that didn't follow the contract properly.)

R=davemoore@chromium.org

Review URL: https://codereview.chromium.org/28983006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229889 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229889