Remove preamble link if annotated step has no extra sections.

scripts/master/chromium_step.py

 # Copyright (c) 2012 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.
 
 """Subclasses of various slave command classes."""
 
 import copy
 import errno
 import json
 import logging
@@ skipping 667 matching lines @@
     if not old_env:
       old_env = {}
     env.update(old_env)
     # Change passed in args (ok as a copy is made internally).
     kwargs['env'] = env
 
     ProcessLogShellStep.__init__(self, *args, **kwargs)
     self.script_observer = AnnotationObserver(self)
     self.addLogObserver('stdio', self.script_observer)
 
+  def _removePreamble(self):
+    """Remove preamble if there is only section.
+
+    'stdio' will be identical to 'preamble' if there is only one annotator
+    section, so it's redundant to show both on the waterfall.
+    """
+    if len(self.script_observer.sections) == 1:
+      self.step_status.logs = [x for x in self.step_status.logs if
+                               x.name != 'preamble']
+
   def interrupt(self, reason):
     self.script_observer.fixupLast(builder.EXCEPTION)
+    self._removePreamble()
     return ProcessLogShellStep.interrupt(self, reason)
 
   def evaluateCommand(self, cmd):
     observer_result = self.script_observer.annotate_status
     # Check if ProcessLogShellStep detected a failure or warning also.
     log_processor_result = ProcessLogShellStep.evaluateCommand(self, cmd)
     return BuilderStatus.combine(observer_result, log_processor_result)
 
   def commandComplete(self, cmd):
     self.script_observer.handleReturnCode(cmd.rc)
+    self._removePreamble()
     return ProcessLogShellStep.commandComplete(self, cmd)
 
 
 class PerfStepAnnotatedCommand(AnnotatedCommand):
   """Annotator command that prepends perf logs when finished."""
 
   def __init__(self, report_link=None, output_dir=None, *args, **kwargs):
     # perf_expectations.json holds performance expectations.  See
     # http://dev.chromium.org/developers/testing/chromium-build-infrastructure/
     # performance-test-plots for more info.
@@ skipping 91 matching lines @@
   def commandComplete(self, cmd):
     if self._report_link and self._output_dir:
       self._MakeOutputDirectory()
       for received_log in self.step_status.getLogs():
         # TODO(xusydoc): do we need to skip 'stdio' and 'preamble' here?
         if log == self._GRAPH_LIST:
           self._SaveGraphInfo(self.getLog(received_log))
         else:
           self._Prepend(received_log, self.getLog(received_log))
     return AnnotatedCommand.commandComplete(self, cmd)