Telemetry: More elegant histogram printing.
Telemetry: More elegant histogram printing.

We now consider the _by_url data important for histograms, and only print out
histograms one by one. So we don't need hacks in perf_tests_helper for printing
out a list of histograms (for which we don't any more know which page they refer to).

BUG=158323
NOTRY=true


Review URL: https://chromiumcodereview.appspot.com/11573008

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@172939 0039d316-1c4b-4281-b951-d872f2087c98

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