This change adds TimelinePowerGraph in Timeline panel, it allows zoom in of power overview, and provides instant power values via mouse move.

BUG=337138

Review URL: https://codereview.chromium.org/212843003

git-svn-id: svn://svn.chromium.org/blink/trunk@170397 bbb929c8-8fbe-4397-9dbb-9b2b20218538