Fix ProcessManagerTest.* flakiness.

extensions/browser/process_manager.cc

 // Copyright 2013 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/browser/process_manager.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 230 matching lines @@
   }
   registrar_.Add(this,
                  extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED,
                  content::Source<BrowserContext>(context));
   registrar_.Add(this,
                  extensions::NOTIFICATION_EXTENSION_HOST_VIEW_SHOULD_CLOSE,
                  content::Source<BrowserContext>(context));
   content::DevToolsAgentHost::AddObserver(this);
 }
 
-ProcessManager::~ProcessManager() = default;
+ProcessManager::~ProcessManager() {
+  content::DevToolsAgentHost::RemoveObserver(this);
+}
 
 void ProcessManager::Shutdown() {
   extension_registry_->RemoveObserver(this);
   CloseBackgroundHosts();
   DCHECK(background_hosts_.empty());
   content::DevToolsAgentHost::RemoveObserver(this);
   site_instance_ = nullptr;
 }
 
 void ProcessManager::RegisterRenderFrameHost(
@@ skipping 624 matching lines @@
   if (extension && !IncognitoInfo::IsSplitMode(extension)) {
     BrowserContext* original_context =
         ExtensionsBrowserClient::Get()->GetOriginalContext(browser_context());
     return ProcessManager::Get(original_context)->GetSiteInstanceForURL(url);
   }
 
   return ProcessManager::GetSiteInstanceForURL(url);
 }
 
 }  // namespace extensions