Add a TestBrowserDialog helper class for testing browser dialogs in a consistent way.

base/test/test_timeouts.h

Index: base/test/test_timeouts.h
diff --git a/base/test/test_timeouts.h b/base/test/test_timeouts.h
index ddaf05b5e0ca583b011f19bb237817aa01a5c953..9d42eb91fe12a0de88e2cf568a30a9d174c8e60d 100644
--- a/base/test/test_timeouts.h
+++ b/base/test/test_timeouts.h
@@ -13,6 +13,9 @@
 // the timeouts for different environments (like Valgrind).
 class TestTimeouts {
  public:
+  // Argument that can be passed on the command line to indicate "no timeout".
+  static constexpr const char kNoTimeoutSwitchValue[] = "-1";
+
   // Initializes the timeouts. Non thread-safe. Should be called exactly once
   // by the test suite.
   static void Initialize();