Update from https://crrev.com/304121

base/observer_list_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/observer_list.h"
 #include "base/observer_list_threadsafe.h"
 
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ skipping 164 matching lines @@
 };
 
 TEST(ObserverListTest, BasicTest) {
   ObserverList<Foo> observer_list;
   Adder a(1), b(-1), c(1), d(-1), e(-1);
   Disrupter evil(&observer_list, &c);
 
   observer_list.AddObserver(&a);
   observer_list.AddObserver(&b);
 
+  EXPECT_TRUE(observer_list.HasObserver(&a));
+  EXPECT_FALSE(observer_list.HasObserver(&c));
+
   FOR_EACH_OBSERVER(Foo, observer_list, Observe(10));
 
   observer_list.AddObserver(&evil);
   observer_list.AddObserver(&c);
   observer_list.AddObserver(&d);
 
   // Removing an observer not in the list should do nothing.
   observer_list.RemoveObserver(&e);
 
   FOR_EACH_OBSERVER(Foo, observer_list, Observe(10));
@@ skipping 336 matching lines @@
   ListDestructor a(observer_list);
   observer_list->AddObserver(&a);
 
   FOR_EACH_OBSERVER(Foo, *observer_list, Observe(0));
   // If this test fails, there'll be Valgrind errors when this function goes out
   // of scope.
 }
 
 }  // namespace
 }  // namespace base