Remove unused properties from ReactMount

(useTouchEvents lives in EventPluginUtils.)

Test Plan: jest

src/browser/ui/ReactMount.js

@@ -212,15 +212,6 @@ function findDeepestCachedAncestor(targetID) {
  * Inside of `container`, the first element rendered is the "reactRoot".
  */
 var ReactMount = {
-  /** Time spent generating markup. */
-  totalInstantiationTime: 0,
-
-  /** Time spent inserting markup into the DOM. */
-  totalInjectionTime: 0,
-
-  /** Whether support for touch events should be initialized. */
-  useTouchEvents: false,
-
   /** Exposed for debugging purposes **/
   _instancesByReactRootID: instancesByReactRootID,