Fix a couple trace issues

- Adding trace tokens since we can be starting/ending traces out of order
- Fixing issue with draw hitting twice causing the trace stack to be
  popped twice
- Fix issue with endFlagOverrides not removing from the stack

Bug: 142803200

Change-Id: I8649b94249910a352f00f2f2c2459c355d2bab00

src/com/android/launcher3/model/LoaderTask.java

@@ -180,7 +180,7 @@ public class LoaderTask implements Runnable {
                     "LoaderTask2 " + this);
         }
 
-        TraceHelper.INSTANCE.beginSection(TAG);
+        Object traceToken = TraceHelper.INSTANCE.beginSection(TAG);
         TimingLogger logger = TestProtocol.sDebugTracing ?
                 new TimingLogger(TAG, "run") {
                     @Override
@@ -281,7 +281,7 @@ public class LoaderTask implements Runnable {
         } finally {
             logger.dumpToLog();
         }
-        TraceHelper.INSTANCE.endSection();
+        TraceHelper.INSTANCE.endSection(traceToken);
     }
 
     public synchronized void stopLocked() {