Add root verification when we try to mark an invalid object.

Now when we try to mark an object not contained by any spaces, We call verify
roots. This prints the root's vreg and method when it finds an invalid root.

Fixed a error in the total paused time statistic.

Change-Id: Id10e4097cce56bc54ee488de32183c18ba3f3780
diff --git a/src/thread_list.cc b/src/thread_list.cc
index 4030be6..09a8de6 100644
--- a/src/thread_list.cc
+++ b/src/thread_list.cc
@@ -502,6 +502,13 @@
   }
 }
 
+void ThreadList::VerifyRoots(Heap::VerifyRootVisitor* visitor, void* arg) const {
+  MutexLock mu(Thread::Current(), *Locks::thread_list_lock_);
+  for (It it = list_.begin(), end = list_.end(); it != end; ++it) {
+    (*it)->VerifyRoots(visitor, arg);
+  }
+}
+
 uint32_t ThreadList::AllocThreadId() {
   MutexLock mu(Thread::Current(), allocated_ids_lock_);
   for (size_t i = 0; i < allocated_ids_.size(); ++i) {