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

base/command_line.cc

 // 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.
 
 #include "base/command_line.h"
 
 #include <algorithm>
 #include <ostream>
 
 #include "base/basictypes.h"
@@ skipping 32 matching lines @@
   return 0;
 }
 
 // Fills in |switch_string| and |switch_value| if |string| is a switch.
 // This will preserve the input switch prefix in the output |switch_string|.
 bool IsSwitch(const CommandLine::StringType& string,
               CommandLine::StringType* switch_string,
               CommandLine::StringType* switch_value) {
   switch_string->clear();
   switch_value->clear();
-  if (GetSwitchPrefixLength(string) == 0)
+  size_t prefix_length = GetSwitchPrefixLength(string);
+  if (prefix_length == 0 || prefix_length == string.length())
     return false;
 
   const size_t equals_position = string.find(kSwitchValueSeparator);
   *switch_string = string.substr(0, equals_position);
   if (equals_position != CommandLine::StringType::npos)
     *switch_value = string.substr(equals_position + 1);
   return true;
 }
 
 // Append switches and arguments, keeping switches before arguments.
@@ skipping 331 matching lines @@
   int num_args = 0;
   wchar_t** args = NULL;
   args = ::CommandLineToArgvW(command_line_string.c_str(), &num_args);
 
   DPLOG_IF(FATAL, !args) << "CommandLineToArgvW failed on command line: "
                          << command_line;
   InitFromArgv(num_args, args);
   LocalFree(args);
 }
 #endif