The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/c23a025e42819769cd3892042c74eed1d9cfa54e

commit c23a025e42819769cd3892042c74eed1d9cfa54e
Author: Jeffrey Li <lijeffrey@chromium.org>
Date: Fri Feb 16 15:24:32 2018

[Findit] Flake Analyzer - Allow for triggering swarming tasks to override isolated input sha

This change introduces a new optional field for triggering swarming tasks against specific
isolated inputs, without affecting existing code. If a sha is not not specified, the reference
swarming task's isolated inputs is used by default (existing behavior).

This is not a permanent solution, as triggering, monitoring, and reporting a swarming task's
results are to be combined into a new pipeline. Rather this is is to unblock testability of
the new Flake Analyzer's pipelines.

Bug:  776958 
Change-Id: I6d1be8159d694e456fea93fa5ada33bc43f13ace
Reviewed-on: https://chromium-review.googlesource.com/740952
Reviewed-by: Chan Li <chanli@chromium.org>
Reviewed-by: Brandon Wylie <wylieb@chromium.org>
Commit-Queue: Jeffrey Li <lijeffrey@chromium.org>

[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py
[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/flake/test/analyze_flake_for_build_number_pipeline_test.py
[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/flake/analyze_flake_for_build_number_pipeline.py
[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/test/trigger_flake_swarming_task_pipeline_test.py
[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/test/trigger_base_swarming_task_pipeline_test.py
[modify] https://crrev.com/c23a025e42819769cd3892042c74eed1d9cfa54e/appengine/findit/waterfall/trigger_swarming_tasks_pipeline.py