PlzNavigate: implement process reuse for ServiceWorkers

content/browser/site_instance_impl.h

 // 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.
 
 #ifndef CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_
 #define CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 46 matching lines @@
   // process-per-site and ServiceWorkers proactively join a process that already
   // contains the site.
   enum class ProcessReusePolicy {
     // In this mode, all instances of the site will be hosted in the same
     // RenderProcessHost.
     PROCESS_PER_SITE,
 
     // In this mode, subframes will be hosted in a designated RenderProcessHost.
     USE_DEFAULT_SUBFRAME_PROCESS,
 
+    // In this mode, the site will be rendered in a RenderProcessHost that is
+    // already in use for the site, either for a pending navigation or a
+    // committed navigation.  If none exists, a new process will be created.  If
+    // multiple such processes exist, ones that have foreground frames are given
+    // priority, and otherwise one is selected randomly.
+    REUSE_PENDING_OR_COMMITTED_SITE,
+
     // By default, a new RenderProcessHost will be created unless the process
     // limit has been reached. The RenderProcessHost reused will be chosen
     // randomly and not based on the site.
     DEFAULT,
   };
 
   void set_process_reuse_policy(ProcessReusePolicy policy) {
     process_reuse_policy_ = policy;
   }
   ProcessReusePolicy process_reuse_policy() const {
@@ skipping 123 matching lines @@
   ProcessReusePolicy process_reuse_policy_;
 
   base::ObserverList<Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteInstanceImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SITE_INSTANCE_IMPL_H_