Add "dumpsys SurfaceFlinger --dispsync"

Dumps the current DispSync state.

Bug 14651879

Change-Id: Ide4e6dbd58b117bc1a6b97b57d10cd92ec86dc84
diff --git a/services/surfaceflinger/main_surfaceflinger.cpp b/services/surfaceflinger/main_surfaceflinger.cpp
index b161480..90e3f7d 100644
--- a/services/surfaceflinger/main_surfaceflinger.cpp
+++ b/services/surfaceflinger/main_surfaceflinger.cpp
@@ -27,7 +27,7 @@
 
 using namespace android;
 
-int main(int argc, char** argv) {
+int main(int, char**) {
     // When SF is launched in its own process, limit the number of
     // binder threads to 4.
     ProcessState::self()->setThreadPoolMaxThreadCount(4);