Enable latency metrics

The metrics were disabled in S because the WeakReference bugs could not
be fixed in time.

Enable them in T, which should allow sufficient time for the other teams
to resolve the WeakReference problems.

Bug: 169866723
Test: adb shell dumpsys input, watch for latency tracker starting to
collect data

Change-Id: I67c4028e7cb8b5e26616ab90b8b60fc871bf4407

core/java/android/view/ViewRootImpl.java

@@ -253,11 +253,11 @@ public final class ViewRootImpl implements ViewParent,
     private static final boolean MT_RENDERER_AVAILABLE = true;
 
     /**
-     * Whether or not to report end-to-end input latency. Disabled temporarily as a
+     * Whether or not to report end-to-end input latency. Can be disabled temporarily as a
      * risk mitigation against potential jank caused by acquiring a weak reference
-     * per frame
+     * per frame.
      */
-    private static final boolean ENABLE_INPUT_LATENCY_TRACKING = false;
+    private static final boolean ENABLE_INPUT_LATENCY_TRACKING = true;
 
     /**
      * Set this system property to true to force the view hierarchy to render