Use underscores to separate words in filenames in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/analyze_baselines_unittest.py

 # Copyright 2016 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.
 
 import optparse
 
-from webkitpy.common.checkout.baselineoptimizer import BaselineOptimizer
+from webkitpy.common.checkout.baseline_optimizer import BaselineOptimizer
 from webkitpy.tool.commands.analyze_baselines import AnalyzeBaselines
 from webkitpy.tool.commands.rebaseline_unittest import BaseTestCase
 
 
 class _FakeOptimizer(BaselineOptimizer):
 
     def read_results_by_directory(self, baseline_name):
         if baseline_name.endswith('txt'):
             return {'LayoutTests/passes/text.html': '123456'}
         return {}
@@ skipping 22 matching lines @@
                 dict(
                     suffixes='png,txt',
                     missing=True,
                     platform=None)),
             ['passes/text.html'],
             self.tool)
         self.assertEqual(self.lines,
                          ['passes/text-expected.png: (no baselines found)',
                           'passes/text-expected.txt:',
                           '  (generic): 123456'])