[content shell] add support for getting tests from the command line.

base/command_line_unittest.cc

Index: base/command_line_unittest.cc
diff --git a/base/command_line_unittest.cc b/base/command_line_unittest.cc
index 310632d01dbdcbd71778bc51dd8584ce51045807..d93ffb89873dca7ae0397203219977e84c74786b 100644
--- a/base/command_line_unittest.cc
+++ b/base/command_line_unittest.cc
@@ -33,6 +33,7 @@ TEST(CommandLineTest, CommandLineConstructor) {
       FILE_PATH_LITERAL("--other-switches=--dog=canine --cat=feline"),
       FILE_PATH_LITERAL("-spaetzle=Crepe"),
       FILE_PATH_LITERAL("-=loosevalue"),
+      FILE_PATH_LITERAL("-"),
       FILE_PATH_LITERAL("FLAN"),
       FILE_PATH_LITERAL("a"),
       FILE_PATH_LITERAL("--input-translation=45--output-rotation"),
@@ -75,11 +76,13 @@ TEST(CommandLineTest, CommandLineConstructor) {
   EXPECT_EQ("45--output-rotation", cl.GetSwitchValueASCII("input-translation"));
 
   const CommandLine::StringVector& args = cl.GetArgs();
-  ASSERT_EQ(7U, args.size());
+  ASSERT_EQ(8U, args.size());
 
   std::vector<CommandLine::StringType>::const_iterator iter = args.begin();
   EXPECT_EQ(FILE_PATH_LITERAL("flim"), *iter);
   ++iter;
+  EXPECT_EQ(FILE_PATH_LITERAL("-"), *iter);
+  ++iter;
   EXPECT_EQ(FILE_PATH_LITERAL("FLAN"), *iter);
   ++iter;
   EXPECT_EQ(FILE_PATH_LITERAL("a"), *iter);