[Findit] Add a sub-pipeline to analyze failures caused by DEPS rolls.

appengine/findit/waterfall/detect_first_failure_pipeline.py

Index: appengine/findit/waterfall/detect_first_failure_pipeline.py
diff --git a/appengine/findit/waterfall/detect_first_failure_pipeline.py b/appengine/findit/waterfall/detect_first_failure_pipeline.py
index a85b05931dda63815bfccebc8cfa133bde0ba89b..95f29ad2113523fb96586cfed5a1dec4b461ec40 100644
--- a/appengine/findit/waterfall/detect_first_failure_pipeline.py
+++ b/appengine/findit/waterfall/detect_first_failure_pipeline.py
@@ -53,7 +53,7 @@ class DetectFirstFailurePipeline(BasePipeline):
             master_name):  # pragma: no cover
           raise pipeline.Retry('Too many download from %s' % master_name)
 
-        # Retrieve build data from build master. 
+        # Retrieve build data from build master.
         build.data = buildbot.GetBuildDataFromBuildMaster(
             build.master_name, build.builder_name, build.build_number,
             self.HTTP_CLIENT)
@@ -236,6 +236,7 @@ class DetectFirstFailurePipeline(BasePipeline):
         'master_name': master_name,
         'builder_name': builder_name,
         'build_number': build_number,
+        'chromium_revision': build_info.chromium_revision,
         'builds': {},
         'failed_steps': [],
     }