mash: Fix shutdown hang in content_browser

content/common/service_manager/service_manager_connection_impl.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 "content/common/service_manager/service_manager_connection_impl.h"
 
 #include <queue>
 #include <utility>
 #include <vector>
 
@@ skipping 195 matching lines @@
   }
 
   void ClearConnectionFiltersOnIOThread() {
     base::AutoLock lock(lock_);
     connection_filters_.clear();
   }
 
   void RemoveConnectionFilterOnIOThread(int filter_id) {
     base::AutoLock lock(lock_);
     auto it = connection_filters_.find(filter_id);
-    // TODO(crbug.com/687247): This DCHECK is hit when the browser is shut down
-    // by the service manager (e.g. in response to an ash crash under mash).
-    // Figure out why.
-    DCHECK(it != connection_filters_.end());
-    connection_filters_.erase(it);
+    // During shutdown the connection filters might have been cleared already
+    // by ClearConnectionFiltersOnIOThread() above, so this id might not exist.
+    if (it != connection_filters_.end())
+      connection_filters_.erase(it);
   }
 
   void OnBrowserConnectionLost() {
     DCHECK(io_thread_checker_.CalledOnValidThread());
     has_browser_connection_ = false;
   }
 
   /////////////////////////////////////////////////////////////////////////////
   // service_manager::Service implementation
 
@@ skipping 312 matching lines @@
 
 void ServiceManagerConnectionImpl::GetInterface(
     service_manager::mojom::InterfaceProvider* provider,
     const std::string& interface_name,
     mojo::ScopedMessagePipeHandle request_handle) {
   provider->GetInterface(interface_name, std::move(request_handle));
 }
 
 }  // namespace content