Check for already existing entry when adding to SiteProcessMap.

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 315 matching lines @@
     LAZY_INSTANCE_INITIALIZER;
 
 // Map of site to process, to ensure we only have one RenderProcessHost per
 // site in process-per-site mode.  Each map is specific to a BrowserContext.
 class SiteProcessMap : public base::SupportsUserData::Data {
  public:
   typedef base::hash_map<std::string, RenderProcessHost*> SiteToProcessMap;
   SiteProcessMap() {}
 
   void RegisterProcess(const std::string& site, RenderProcessHost* process) {
-    map_[site] = process;
+    // There could already exist a site to process mapping due to races between
+    // two WebContents with blank SiteInstances. If that occurs, keeping the
+    // exising entry and not overwriting it is a predictable behavior that is
+    // safe.
+    SiteToProcessMap::iterator i = map_.find(site);
+    if (i == map_.end())
+      map_[site] = process;
   }
 
   RenderProcessHost* FindProcess(const std::string& site) {
     SiteToProcessMap::iterator i = map_.find(site);
     if (i != map_.end())
       return i->second;
     return NULL;
   }
 
   void RemoveProcess(RenderProcessHost* host) {
@@ skipping 2719 matching lines @@
   LOG(ERROR) << "Terminating render process for bad Mojo message: " << error;
 
   // The ReceivedBadMessage call below will trigger a DumpWithoutCrashing.
   // Capture the error message in a crash key value.
   base::debug::ScopedCrashKey error_key_value("mojo-message-error", error);
   bad_message::ReceivedBadMessage(render_process_id,
                                   bad_message::RPH_MOJO_PROCESS_ERROR);
 }
 
 }  // namespace content