Add two command-line parameters and one bug fix for the layout test analyzer.

media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py

Index: media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py
diff --git a/media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py b/media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py
index 3d29925f02e80e36717176b82bc99031494057c0..deeb34845c130366952488aae72524561297258b 100644
--- a/media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py
+++ b/media/tools/layout_tests/layouttest_analyzer_helpers_unittest.py
@@ -15,10 +15,20 @@ class TestLayoutTestAnalyzerHelpers(unittest.TestCase):
 
   def testFindLatestTime(self):
     time_list = ['2011-08-18-19', '2011-08-18-22', '2011-08-18-21',
-                 '2012-01-11-21']
+                 '2012-01-11-21', '.foo']
     self.assertEquals(layouttest_analyzer_helpers.FindLatestTime(time_list),
                       '2012-01-11-21')
 
+  def testFindLatestTimeWithEmptyList(self):
+    time_list = []
+    self.assertEquals(layouttest_analyzer_helpers.FindLatestTime(time_list),
+                      None)
+
+  def testFindLatestTimeWithNoValidStringInList(self):
+    time_list = ['.foo1', '232232']
+    self.assertEquals(layouttest_analyzer_helpers.FindLatestTime(time_list),
+                      None)
+
   def GenerateTestDataWholeAndSkip(self):
     """You should call this method if you want to generate test data."""
     file_path = os.path.join('test_data', 'base')