Don't add or remove verifiers if aborting

Prevents deadlock if marking verifier roots fails when we attempt to
dump the stack traces. The deadlock occurs from FindLocksAtDexPC
since this allocates a new verifier then adds / removes it from the
method_verifiers_ array.

Bug: 18651054
Change-Id: Ia9b9470ce5e4ac20bfbb39bef0283974cf487765
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 07e2ec0..e91f7c0 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -1380,12 +1380,18 @@
 
 void Runtime::AddMethodVerifier(verifier::MethodVerifier* verifier) {
   DCHECK(verifier != nullptr);
+  if (gAborting) {
+    return;
+  }
   MutexLock mu(Thread::Current(), method_verifier_lock_);
   method_verifiers_.insert(verifier);
 }
 
 void Runtime::RemoveMethodVerifier(verifier::MethodVerifier* verifier) {
   DCHECK(verifier != nullptr);
+  if (gAborting) {
+    return;
+  }
   MutexLock mu(Thread::Current(), method_verifier_lock_);
   auto it = method_verifiers_.find(verifier);
   CHECK(it != method_verifiers_.end());