[telemetry] Remove perf/perf_tools.

Modify the sys.path directly in run_measurement rather than in perf_tools/__init__.py. This is more explicit behavior.
Modify run_measurement bootstrap to make all paths relative to itself rather than to perf_tools.
Modify bootstrap_deps to include the entire tools/perf/ folder. We've had problems in the past where adding new subdirs to perf/ would break things.


BUG=311380
TEST=Modified run_measurement to use the local telemetry_bootstrap.py and src/tools/perf/perf_tools. Then ran it outside of a Chromium checkout twice. Also ran run_measurement --print-bootstrap-deps

Review URL: https://codereview.chromium.org/107113004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239318 0039d316-1c4b-4281-b951-d872f2087c98
cc: Clean up tick times used for LayerAnimationControllerTests

This makes LayerAnimationControllerTests no longer tick controllers
at time 0, since Animation::has_set_start_time returns false when
an animation's start time is 0.

To prevent future tests from running into this problem, this also
adds a DCHECK to LayerAnimationController::Animate.

BUG=None

Review URL: https://codereview.chromium.org/107223003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239319 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239319