Fix failing performace tests

Track contents drawing function is draw_() instead of drawTrackContents_().

Call to invalid function drawTrackContents_() is causing failure of performance tests:
tracing.tracks.drawing_container_perf_test.draw_softwareCanvas_1
tracing.tracks.drawing_container_perf_test.draw_softwareCanvas_10
tracing.tracks.drawing_container_perf_test.draw_softwareCanvas_100

drawTrackContents_() was renamed to draw_() as part of revision 1544 - Add collapsing to most tracks in the timeline

[1] https://code.google.com/p/trace-viewer/source/diff?spec=svn1544&r=1544&format=side&path=/trunk/trace_viewer/tracing/tracks/drawing_container.html

R=dsinclair@chromium.org
Merge pull request #5 from kphanee/fix_perf_tests

Fix failing performace tests