Increase time precision in top-down and bottom-up profile views to 0.1ms

No that we support hi-res profiling with 0.1ms sampling interval we should show self and total time with 0.1ms precision.

BUG=307741

Review URL: https://codereview.chromium.org/27492002

git-svn-id: svn://svn.chromium.org/blink/trunk@159772 bbb929c8-8fbe-4397-9dbb-9b2b20218538