[Telemetry] Fix image_decoding_measurement timeout.

util.WaitFor polls which is not appropriate for PerformActionAndWaitForNavigate.

Since DispatchNotifications blocks in recv until it gets some data, there is no
need to poll at an interval. Instead, we should call recv again as soon as
possible after dispatching a notification.

In the case of the image decoding measurement, it runs timeline recording. There
were so many timeline messages to receive that we were not always getting to the
important Page.navigate message before timing out.

Example:
http://build.chromium.org/p/chromium.perf/builders/Linux%20Perf%20%281%29/builds/27098

BUG=314375

Review URL: https://codereview.chromium.org/47013004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232959 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232959