Currently when a try run fails, you get the following final step;
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Failure reason ( 4 ms ) Failure reason
  stdio
  reason
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See https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_rel_ng/414721 for example.

There are numerous failings here;

 * The step is green despite it indicating that the whole thing failed.
 * Clicking the stdio link gives you a message about "log dog". 
 * Clicking the reason link gives you;
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3 out of 3 aggregated steps failed. Failures: Step('unit_tests (retry summary)') failed with return_code 1, Step('browser_side_navigation_unit_tests (retry summary)') failed with return_code 1, Step('site_per_process_unit_tests (retry summary)') failed with return_code 1
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This is a horrible UI. I would be surprised if people even looked at this step...

Bunch of important questions;

 * Why do I have to click something to see the important message?
 * Why doesn't the message include links to the failures?
 * Why do I care about the return code?
 * What is the action item from seeing this output?

A developer shouldn't need to understand how recipies or buildbot works to understand the failure.