libqdutils: Add synchronization to idle invalidator

Protect invalidator data from accessing multiple threads
asynchronously. Composition thread and idle invalidator
threads could access at same time. Add locking to protect
invalidator class  member variables.

Change-Id: I568ec367958c88f70f7aa4e6917abd53830adfd3
diff --git a/libqdutils/idle_invalidator.h b/libqdutils/idle_invalidator.h
index 82b1ac0..abd9b29 100644
--- a/libqdutils/idle_invalidator.h
+++ b/libqdutils/idle_invalidator.h
@@ -32,6 +32,7 @@
 
 #include <cutils/log.h>
 #include <utils/threads.h>
+#include <gr.h>
 
 typedef void (*InvalidatorHandler)(void*);
 
@@ -41,6 +42,7 @@
     unsigned int mSleepTime;
     static InvalidatorHandler mHandler;
     static android::sp<IdleInvalidator> sInstance;
+    mutable Locker mLock;
 
     public:
     IdleInvalidator();