[DevTools] Add uiTest.testSettings.

Source/devtools/front_end/Runtime.js

Index: Source/devtools/front_end/Runtime.js
diff --git a/Source/devtools/front_end/Runtime.js b/Source/devtools/front_end/Runtime.js
index 6b472216a5aba351c7271ea49700dd1d8bfcb0da..41e7cd7dafc1dd1e4b751e1e925e1d7eada7b87b 100644
--- a/Source/devtools/front_end/Runtime.js
+++ b/Source/devtools/front_end/Runtime.js
@@ -991,6 +991,13 @@ Runtime.ExperimentsSupport.prototype = {
         this._enabledTransiently[experimentName] = true;
     },
 
+    clearForTest: function()
+    {
+        this._experiments = [];
+        this._experimentNames = {};
+        this._enabledTransiently = {};
+    },
+
     cleanUpStaleExperiments: function()
     {
         var experimentsSetting = Runtime._experimentsSetting();