[Extensions Bindings] Allow event listener unregistration in handling

extensions/renderer/event_emitter.cc

 // Copyright 2016 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 "extensions/renderer/event_emitter.h"
 
 #include <algorithm>
 
 #include "gin/object_template_builder.h"
 #include "gin/per_context_data.h"
@@ skipping 16 matching lines @@
       .SetMethod("hasListeners", &EventEmitter::HasListeners)
       // The following methods aren't part of the public API, but are used
       // by our custom bindings and exposed on the public event object. :(
       // TODO(devlin): Once we convert all custom bindings that use these,
       // they can be removed.
       .SetMethod("dispatch", &EventEmitter::Dispatch);
 }
 
 void EventEmitter::Fire(v8::Local<v8::Context> context,
                         std::vector<v8::Local<v8::Value>>* args) {
-  for (const auto& listener : listeners_) {
-    run_js_.Run(listener.Get(context->GetIsolate()), context, args->size(),
-                             args->data());
-  }
+  // We create a local copy of listeners_ since the array can be modified during
+  // handling.
+  std::vector<v8::Local<v8::Function>> listeners;
+  listeners.reserve(listeners_.size());
+  for (const auto& listener : listeners_)
+    listeners.push_back(listener.Get(context->GetIsolate()));
+
+  for (const auto& listener : listeners)
+    run_js_.Run(listener, context, args->size(), args->data());
 }
 
 void EventEmitter::AddListener(gin::Arguments* arguments) {
   v8::Local<v8::Function> listener;
   if (!arguments->GetNext(&listener))
     return;
 
   v8::Local<v8::Object> holder;
   CHECK(arguments->GetHolder(&holder));
   CHECK(!holder.IsEmpty());
@@ skipping 38 matching lines @@
     }
   }
   if (!valid) {
     arguments->ThrowTypeError("Invalid invocation");
     return;
   }
   Fire(context, &v8_args);
 }
 
 }  // namespace extensions