Change ExecuteJavaScript* helper functions in browser_test_utils.{h,cc}

content/browser/fileapi/file_system_browsertest.cc

Index: content/browser/fileapi/file_system_browsertest.cc
diff --git a/content/browser/fileapi/file_system_browsertest.cc b/content/browser/fileapi/file_system_browsertest.cc
index be47ac7f151cbffaf42c92470e4c37e8e46ba667..e01f08b533a6c2fdac1ddfa4f6ae873ff448a158 100644
--- a/content/browser/fileapi/file_system_browsertest.cc
+++ b/content/browser/fileapi/file_system_browsertest.cc
@@ -42,8 +42,10 @@ class FileSystemBrowserTest : public ContentBrowserTest {
     if (result != "pass") {
       std::string js_result;
       ASSERT_TRUE(ExecuteJavaScriptAndExtractString(
-          the_browser->web_contents()->GetRenderViewHost(), L"",
-          L"window.domAutomationController.send(getLog())", &js_result));
+          the_browser->web_contents()->GetRenderViewHost(),
+          std::string(),
+          "window.domAutomationController.send(getLog())",
+          &js_result));
       FAIL() << "Failed: " << js_result;
     }
   }