Add a metrics extensions API....

chrome/test/test_launcher/out_of_proc_test_runner.cc

 // Copyright (c) 2009 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 <string>
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/process_util.h"
 
@@ skipping 66 matching lines @@
     return new OutOfProcTestRunner();
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OutOfProcTestRunnerFactory);
 };
 
 void PrintUsage() {
   fprintf(stdout, "Runs tests using the gtest framework, each test being run in"
       " its own process.\nAny gtest flags can be specified.\n"
-      "  --single-process\n    Runs the tests and the launcher in the same "
+      "  --single_process\n    Runs the tests and the launcher in the same "
       "process. Useful for debugging a\n    specific test in a debugger\n  "
       "--help\n    Shows this message.\n  --gtest_help\n    Shows the gtest "
       "help message\n");
 }
 
 }  // namespace
 
 int main(int argc, char** argv) {
   CommandLine::Init(argc, argv);
   const CommandLine* command_line = CommandLine::ForCurrentProcess();
 
   if (command_line->HasSwitch(kHelpFlag)) {
     PrintUsage();
     return 0;
   }
 
+  if (command_line->HasSwitch(kSingleProcessFlag)) {
+    fprintf(stdout,
+            "\n  Did you mean --%s instead? (note underscore)\n\n",
+            kSingleProcessAltFlag);
+  }
+
   if (command_line->HasSwitch(kChildProcessFlag) ||
       command_line->HasSwitch(kSingleProcessFlag) ||
       command_line->HasSwitch(kSingleProcessAltFlag) ||
       command_line->HasSwitch(kGTestListTestsFlag) ||
       command_line->HasSwitch(kGTestHelpFlag)) {
     return ChromeTestSuite(argc, argv).Run();
   }
 
   fprintf(stdout,
           "Starting tests...\nIMPORTANT DEBUGGING NOTE: each test is run inside"
           " its own process.\nFor debugging a test inside a debugger, use the "
-          "--single-process and\n--gtest_filter=<your_test_name> flags.\n");
+          "--single_process and\n--gtest_filter=<your_test_name> flags.\n");
   OutOfProcTestRunnerFactory test_runner_factory;
   return tests::RunTests(test_runner_factory) ? 0 : 1;
 }