Lock drm plugin API calls globally, not per MediaDrm instance

Change-Id: I062c662a440a1becccd248c3b8ddf711c51e53cc
related-to-bug: 18394494
related-to-bug: 19664283
diff --git a/media/libmediaplayerservice/Drm.cpp b/media/libmediaplayerservice/Drm.cpp
index 8ca8769..d55482d 100644
--- a/media/libmediaplayerservice/Drm.cpp
+++ b/media/libmediaplayerservice/Drm.cpp
@@ -52,6 +52,7 @@
 KeyedVector<Vector<uint8_t>, String8> Drm::mUUIDToLibraryPathMap;
 KeyedVector<String8, wp<SharedLibrary> > Drm::mLibraryPathToOpenLibraryMap;
 Mutex Drm::mMapLock;
+Mutex Drm::mLock;
 
 static bool operator<(const Vector<uint8_t> &lhs, const Vector<uint8_t> &rhs) {
     if (lhs.size() < rhs.size()) {
diff --git a/media/libmediaplayerservice/Drm.h b/media/libmediaplayerservice/Drm.h
index c4013b8..056723c 100644
--- a/media/libmediaplayerservice/Drm.h
+++ b/media/libmediaplayerservice/Drm.h
@@ -143,7 +143,7 @@
     virtual void binderDied(const wp<IBinder> &the_late_who);
 
 private:
-    mutable Mutex mLock;
+    static Mutex mLock;
 
     status_t mInitCheck;