[Findit] Add three sub-pipelines to analyze build failure.

appengine/findit/waterfall/identify_culprit_pipeline.py

Index: appengine/findit/waterfall/identify_culprit_pipeline.py
diff --git a/appengine/findit/waterfall/identify_culprit_pipeline.py b/appengine/findit/waterfall/identify_culprit_pipeline.py
new file mode 100644
index 0000000000000000000000000000000000000000..746ee55c0544d7d8475dd565876ad767f90b8ca9
--- /dev/null
+++ b/appengine/findit/waterfall/identify_culprit_pipeline.py
@@ -0,0 +1,38 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+from model.build_analysis import BuildAnalysis
+from model.build_analysis_status import BuildAnalysisStatus
+from waterfall import build_failure_analysis
+from waterfall.base_pipeline import BasePipeline
+
+
+class IdentifyCulpritPipeline(BasePipeline):
+  """A pipeline to identify culprit CLs for a build failure."""
+
+  # Arguments number differs from overridden method - pylint: disable=W0221
+  def run(self, failure_info, change_logs, signals):
+    """
+    Args:
+      failure_info (dict): Output of pipeline DetectFirstFailurePipeline.
+      change_logs (dict): Output of pipeline PullChangelogPipeline.
+      signals (dict): Output of pipeline ExtractSignalPipeline.
+
+    Returns:
+      The same dict as the returned value of function
+      build_failure_analysis.AnalyzeBuildFailure.
+    """
+    master_name = failure_info['master_name']
+    builder_name = failure_info['builder_name']
+    build_number = failure_info['build_number']
+
+    analysis_result = build_failure_analysis.AnalyzeBuildFailure(
+        failure_info, change_logs, signals)
+    analysis = BuildAnalysis.GetBuildAnalysis(
+        master_name, builder_name, build_number)
+    analysis.result = analysis_result
+    analysis.status = BuildAnalysisStatus.ANALYZED
+    analysis.put()
+
+    return analysis_result