ResizeObserver: Olipan C++ tests

third_party/WebKit/Source/core/observer/ResizeObserverController.h

Index: third_party/WebKit/Source/core/observer/ResizeObserverController.h
diff --git a/third_party/WebKit/Source/core/observer/ResizeObserverController.h b/third_party/WebKit/Source/core/observer/ResizeObserverController.h
index 49265289100c0c142bd2fa88d7d7cf2deb1e378d..a3b7a03a1d5bb83febd1b93f7d4c0d64f55e8fe0 100644
--- a/third_party/WebKit/Source/core/observer/ResizeObserverController.h
+++ b/third_party/WebKit/Source/core/observer/ResizeObserverController.h
@@ -38,6 +38,9 @@ public:
 
     DECLARE_TRACE();
 
+    // For testing only.
+    const HeapHashSet<WeakMember<ResizeObserver>>& observers() { return m_observers; }
+
 private:
     // Active observers
     HeapHashSet<WeakMember<ResizeObserver>> m_observers;