PrependWrapper is platform-specific, so it should take a platform string.

chrome/test/ui/ui_test.cc

Index: chrome/test/ui/ui_test.cc
diff --git a/chrome/test/ui/ui_test.cc b/chrome/test/ui/ui_test.cc
index 48849a31ffb0abede4ac2db574967e3c0a979f73..bef38015727fc24f8c22017b3a1234978bec7a8b 100644
--- a/chrome/test/ui/ui_test.cc
+++ b/chrome/test/ui/ui_test.cc
@@ -1209,7 +1209,7 @@ bool UITestBase::LaunchBrowserHelper(const CommandLine& arguments,
   // commandline with a special prefix to invoke the special environment.
   const char* browser_wrapper = getenv("BROWSER_WRAPPER");
   if (browser_wrapper) {
-    command_line.PrependWrapper(ASCIIToWide(browser_wrapper));
+    command_line.PrependWrapper(browser_wrapper);
     LOG(INFO) << "BROWSER_WRAPPER was set, prefixing command_line with "
               << browser_wrapper;
   }