Explicitly pass Thread::Current to MutexLock and Alloc.

Change-Id: I8b75bc0617915465f102815b32306aa7760dcae4
diff --git a/src/signal_catcher.cc b/src/signal_catcher.cc
index 8376bb6..b6f6a41 100644
--- a/src/signal_catcher.cc
+++ b/src/signal_catcher.cc
@@ -85,12 +85,12 @@
 }
 
 void SignalCatcher::SetHaltFlag(bool new_value) {
-  MutexLock mu(lock_);
+  MutexLock mu(Thread::Current(), lock_);
   halt_ = new_value;
 }
 
 bool SignalCatcher::ShouldHalt() {
-  MutexLock mu(lock_);
+  MutexLock mu(Thread::Current(), lock_);
   return halt_;
 }