Bug 1448439 - Fix unified build bustage. r=kats

MozReview-Commit-ID: 3HAcjOB1tjn

--HG--
extra : rebase_source : ef68f50b01af2ba5a00f76fd2f5e3fd01bfead6a

gfx/layers/ipc/LayerTreeOwnerTracker.h

@@ -8,6 +8,7 @@
 #define mozilla_layers_LayerTreeOwnerTracker_h
 
 #include "base/process.h"  // for base::ProcessId
+#include "LayersTypes.h"   // for LayersId
 #include "mozilla/Mutex.h" // for mozilla::Mutex
 
 #include <functional>