Avoid handle-less methods in ClassLinker::LinkInterfaceMethods().

There were some handle-less methods in local variables across
potential GC points.

Bug: 12687968

Change-Id: I786fbaadf7a52e98194080c67c90fc1c35060d59
diff --git a/runtime/method_helper.h b/runtime/method_helper.h
index f71d273..8150456 100644
--- a/runtime/method_helper.h
+++ b/runtime/method_helper.h
@@ -41,6 +41,11 @@
     return method_->GetInterfaceMethodIfProxy();
   }
 
+  // GetMethod() != Get() for proxy methods.
+  mirror::ArtMethod* Get() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+    return method_.Get();
+  }
+
   mirror::String* GetNameAsString(Thread* self) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   const char* GetShorty() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {