Clean up Fence a little.

Test: Cleanup patch only. Fences still work.

Change-Id: I65e5cdf5e3c067bc475c085ab6d3577d9753231c
diff --git a/libs/gui/FrameTimestamps.cpp b/libs/gui/FrameTimestamps.cpp
index 46ca974..fb242f7 100644
--- a/libs/gui/FrameTimestamps.cpp
+++ b/libs/gui/FrameTimestamps.cpp
@@ -18,6 +18,7 @@
 
 #include <cutils/compiler.h>  // For CC_[UN]LIKELY
 #include <inttypes.h>
+#include <utils/Log.h>
 #include <utils/String8.h>
 
 #include <algorithm>