Add trace parser for SurfaceFlinger graphics frame events

Test: From perfetto folder:
tools/diff_test_trace_processor.py --trace-descriptor=$PERFETTO_OUT/gen/protos/perfetto/trace/trace.descriptor $PERFETTO_OUT/trace_processor_shell

Change-Id: I74064889d7260b7aae55f4f147fd5c65294eaf16
diff --git a/src/trace_processor/trace_storage.h b/src/trace_processor/trace_storage.h
index d88b0b0..64918ff 100644
--- a/src/trace_processor/trace_storage.h
+++ b/src/trace_processor/trace_storage.h
@@ -1254,6 +1254,9 @@
     return &virtual_track_slices_;
   }
 
+  const GpuSlices& gpu_track_slices() const { return gpu_track_slices_; }
+  GpuSlices* mutable_gpu_track_slices() { return &gpu_track_slices_; }
+
   const CounterDefinitions& counter_definitions() const {
     return counter_definitions_;
   }
@@ -1312,6 +1315,9 @@
     return &heap_profile_allocations_;
   }
 
+  const GpuTracks& gpu_tracks() const { return gpu_tracks_; }
+  GpuTracks* mutable_gpu_tracks() { return &gpu_tracks_; }
+
   const StringPool& string_pool() const { return string_pool_; }
 
   // |unique_processes_| always contains at least 1 element becuase the 0th ID