Remove high-overhead low-signal trace section

Bug: 28519669

This trace tag makes shadows look way more expensive
than they actually are, particularly troublesome
when tracing things with large number of shadows.

Change-Id: Ib6558b1388edd4b006ec15127470cb9ab563f954

libs/hwui/thread/Task.h

@@ -38,7 +38,6 @@ public:
     virtual ~Task() { }
 
     T getResult() const {
-        ScopedTrace tracer(ATRACE_TAG_VIEW, "waitForTask");
         return mFuture->get();
     }