Ensure all pyauto perf tests in perf.py output a descriptive graph name.
Ensure all pyauto perf tests in perf.py output a descriptive graph name.

Several of the perf tests in perf.py outputted only default graph names.
This change ensures all perf tests output descriptive graph names.  The
graph names will soon be used to graph the results on Chrome buildbot
using Chrome's graphing infrastructure.

This change also ensures that graph names are all lower-case with words
separated by underscores.  This seems to more closely follow the format
of existing Chrome perf graphs.  Previously, the graph names were given
in camelCase.

BUG=None
TEST=None

Review URL: https://chromiumcodereview.appspot.com/9919001

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@130502 0039d316-1c4b-4281-b951-d872f2087c98

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