Repro steps:
1) """./tools/perf/run_benchmark --browser=canary power.steady_state"""
Once the test starts running, you can Ctr-C out. [Read: I'm too lazy to find the more concise command to download the relevant WPR file]

2) """third_party/catapult/./telemetry/third_party/web-page-replay/replay.py ./tools/perf/page_sets/data/idle_after_loading_stories_002.wpr"""
Start the WPR server.

3) """/Applications/Google\ Chrome\ Canary.app/Contents/MacOS/Google\ Chrome\ Canary --user-data-dir=/tmp/a2 --host-resolver-rules="MAP * 127.0.0.1,EXCLUDE localhost" --ignore-certificate-errors"""

4) Navigate to http://bgr.com

5) Make a timeline recording. Note that this function call repeats every ~30ms
"""
t @ i.js?ver=4.5.3-20160628:1
"""

6) Pretty print i.js. Note that breakpoint on line 1 doesn't trigger.

7) Break on line 178 [search for "eu =", break on "var t = Date.now()"]
Note that this is hit every frame.