Fix: RefCountInterface: Make AddRef() and Release() const

webrtc/base/refcount.h

Index: webrtc/base/refcount.h
diff --git a/webrtc/base/refcount.h b/webrtc/base/refcount.h
index dbad2eba76c3763ae9a09dd8b1e9fd58f372e0b8..55ce23a348b68a84ce362d98f85c0f871725303a 100644
--- a/webrtc/base/refcount.h
+++ b/webrtc/base/refcount.h
@@ -95,11 +95,11 @@ class RefCountedObject : public T {
   : T(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11), ref_count_(0) {
   }
 
-  int AddRef() const override {
+  virtual int AddRef() const {
     return AtomicOps::Increment(&ref_count_);
   }
 
-  int Release() const override {
+  virtual int Release() const {
     int count = AtomicOps::Decrement(&ref_count_);
     if (!count) {
       delete this;