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

appengine/findit/model/step.py

+# Copyright 2014 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 google.appengine.ext import ndb
+
+from model.base_build_model import BaseBuildModel
+
+
+class Step(BaseBuildModel):
+  """Represents a step in a build cycle of a builder in a waterfall."""
+
+  @staticmethod
+  def CreateKey(
+      master_name, builder_name, build_number, step_name):  # pragma: no cover
+    build_id = BaseBuildModel.CreateBuildId(
+        master_name, builder_name, build_number)
+    return ndb.Key('Build', build_id, 'Step', step_name)
+
+  @staticmethod
+  def CreateStep(
+      master_name, builder_name, build_number, step_name):  # pragma: no cover
+    return Step(
+        key=Step.CreateKey(master_name, builder_name, build_number, step_name))
+
+  @staticmethod
+  def GetStep(
+      master_name, builder_name, build_number, step_name):  # pragma: no cover
+    return Step.CreateKey(
+        master_name, builder_name, build_number, step_name).get()
+
+  log_data = ndb.JsonProperty(indexed=False, compressed=True)