[DevTools] use debug_frontend flag in content_shell for tests

content/shell/browser/layout_test/layout_test_devtools_frontend.cc

Index: content/shell/browser/layout_test/layout_test_devtools_frontend.cc
diff --git a/content/shell/browser/layout_test/layout_test_devtools_frontend.cc b/content/shell/browser/layout_test/layout_test_devtools_frontend.cc
index 63a7809f015c0a93372c9a99a8e6899546319532..7a047dafcd2e6274f7b592c4190220b1a883a45c 100644
--- a/content/shell/browser/layout_test/layout_test_devtools_frontend.cc
+++ b/content/shell/browser/layout_test/layout_test_devtools_frontend.cc
@@ -53,10 +53,16 @@ GURL LayoutTestDevToolsFrontend::GetDevToolsPathAsURL(
       dir_exe.AppendASCII("resources/inspector/inspector.html");
 
   GURL result = net::FilePathToFileURL(dev_tools_path);
-  if (!settings.empty())
-    result = GURL(base::StringPrintf("%s?settings=%s&experiments=true",
-                                     result.spec().c_str(),
-                                     settings.c_str()));
+  if (!settings.empty()) {
+    std::string queryParams =
+        base::StringPrintf("%s?settings=%s&experiments=true",
+                           result.spec().c_str(), settings.c_str());
+#if defined(DEBUG_DEVTOOLS)
+    queryParams += "&debugFrontend=true";

[dgozman, 2016/01/27 02:39:14]

Should we append debugFrontend and experiments even when no settings were
passed?

[kozy, 2016/01/27 18:54:55]

Done.

+#endif  // defined(DEBUG_DEVTOOLS)
+
+    result = GURL(queryParams);
+  }
   return result;
 }