Here is an example of how this works.
Case:
  Entire regression range is: (r0, r10].
  Heuristics-based results are: [r5]
  Actual culprit is: r5

Currently without heuristics-based results, the recipe findit/chromium/compile runs at 5 revisions r1, r2, r3, r4, and r5 to identify the culprit r5.

With the heuristics-based results, the recipe could divide the entire regression range into two smaller ranges:
  range1: r4, and [r5, r6, r7, r8, r9, r10]
  range2: r0, and [r1, r2, r3]
The recipe checks range1 first, and it runs compile only at 2 revision r4 (pass) and then r5 (fail) to identify the culprit r5.

In this way, it runs less rounds of compile and as a result speeds up the culprit finding.

The CL was landed. https://codereview.chromium.org/1869223002/

Oops, close it too quick.

There is still a change needed on Findit side.

The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra.git/+/a9b4358417b652c85f94235d86c7542246a76610

commit a9b4358417b652c85f94235d86c7542246a76610
Author: stgao <stgao@chromium.org>
Date: Tue Apr 12 22:11:25 2016

[Findit] Check the explicit culprit from try-job if it is set.

BUG= chromium:596967 

Review URL: https://codereview.chromium.org/1882273002

[modify] https://crrev.com/a9b4358417b652c85f94235d86c7542246a76610/appengine/findit/waterfall/identify_try_job_culprit_pipeline.py
[modify] https://crrev.com/a9b4358417b652c85f94235d86c7542246a76610/appengine/findit/waterfall/test/identify_try_job_culprit_pipeline_test.py

The corresponding change on recipe side was landed as  https://codereview.chromium.org/1881223002/

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/tools/build.git/+/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b

commit 37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b
Author: stgao@chromium.org <stgao@chromium.org>
Date: Tue Apr 12 22:08:16 2016

[Findit] Set culprit and infra failure explicitly.

If suspected revisions from heuristic analysis are passed over to the recipe, there might be more than one revision with compile failures. Thus set the culprit explicitly if found.

BUG= chromium:596967 

Review URL: https://codereview.chromium.org/1881223002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/build@299873 0039d316-1c4b-4281-b951-d872f2087c98

[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/compile_failed.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/failed_compile_upon_infra_failure_goma_build_error.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/failed_compile_upon_infra_failure_goma_ping_failure.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/failed_compile_upon_infra_failure_goma_setup_failure.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/find_culprit_as_first_revision_of_entire_range.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/find_culprit_at_first_revision_of_a_sub_range.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/find_culprit_in_middle_of_a_sub_range.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.expected/find_culprit_in_second_sub_range.json
[modify] https://crrev.com/37ab5bcdc6f6f9bfdc45f8e32785ab0a386ff98b/scripts/slave/recipes/findit/chromium/compile.py