Add HWC composition queueing trace event

As a part of the frame lifecycle, adding HWC_COMPOSITION_QUEUED event
from within SurfaceFlinger.

Test: Build, flash and run GAPID on any app
Bug: 140236090
Change-Id: I7277af4fc0368a684993ac44bb9be6668f6d2090
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index 1388612..3bd9545 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -601,6 +601,8 @@
 
     virtual sp<GraphicBuffer> getBuffer() const { return nullptr; }
 
+    virtual uint64_t getCurrentFrameNumber() const { return mCurrentFrameNumber; }
+
     /*
      * Returns if a frame is ready
      */