systrace: add support for older platform versions.

This change re-adds the old Systrace script from before JB MR2 and exec's it
from when it detects that the device's SDK-version is less than 18.
This change also modifies the pre-JB-MR2 script to generate HTML that is
compatible with the latest script.js and style.css.

Change-Id: I29c3327e95f8fd0a4aab730845abac84e66848ef
2 files changed