The following revision refers to this bug:
  https://chromium.googlesource.com/infra/infra/+/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb

commit f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb
Author: Jeffrey Li <lijeffrey@google.com>
Date: Thu Jan 11 01:22:16 2018

[Findit] Flake Analyzer - NextCommitPositionPipeline

New pipeline for determining the next commit position flake analyzer
should run. This pipeline is responsible for calling into the lookback
algorithm and deciding what to do with the returned commit positions to
be analyzed. Biases towards as late commit positions as possible, and
attempts to reuse build artifacts whenever possible.

1. Takes existing data points and passes them to lookback_algorithm.
2. Maps returned commit position from lookback_algorithm to the nearest
   neighboring builds, checking if either has already been analyzed and
   returns the corresponding commit position to the unanalyzed build.
3. If both neighboring builds' commit positions have already been
   analyzed, run heuristic analysis to generate suspects. TODO: check
   for valid build artifacts before proceeding.
4. If suspects are available, return commit positions of suspects (TODO).
5. If no suspects and both neighboring builds are already analyzed,
   returns the suggested commit position by the lookback_algorithm
   directly signifying the calling pipelines that compile is needed.


Bug:  798626 
Change-Id: Ibe303ed5cd322eee684a3251dc040a7cce9f6c3c
Reviewed-on: https://chromium-review.googlesource.com/848308
Reviewed-by: Brandon Wylie <wylieb@chromium.org>
Commit-Queue: Jeffrey Li <lijeffrey@chromium.org>

[add] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/dto/int_range.py
[add] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/pipelines/flake_failure/test/next_commit_position_pipeline_test.py
[modify] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/model/flake/test/master_flake_analysis_test.py
[add] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/pipelines/flake_failure/next_commit_position_pipeline.py
[modify] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/model/flake/master_flake_analysis.py
[modify] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/waterfall/flake/flake_constants.py
[modify] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/gae_libs/pipelines.py
[add] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/services/flake_failure/next_commit_position_utils.py
[modify] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/waterfall/flake/recursive_flake_try_job_pipeline.py
[add] https://crrev.com/f1123e9a7364cbf0f9f6ed4875ffb63daadbe8cb/appengine/findit/services/flake_failure/test/next_commit_position_utils_test.py