Addressing minor review comments in ExtensionProcessManager...

chrome/browser/extensions/extension_process_manager.cc

Index: chrome/browser/extensions/extension_process_manager.cc
===================================================================
--- chrome/browser/extensions/extension_process_manager.cc	(revision 21073)
+++ chrome/browser/extensions/extension_process_manager.cc	(working copy)
@@ -85,11 +85,14 @@
 }
 
 void ExtensionProcessManager::RegisterExtensionProcess(
-    std::string extension_id, int process_id) {
+    const std::string& extension_id, int process_id) {
   ProcessIDMap::const_iterator it = process_ids_.find(extension_id);
   if (it != process_ids_.end() && (*it).second == process_id)
     return;
 
+  // Extension ids should get removed from the map before the process ids get
+  // reused from a dead renderer.
+  DCHECK(it == process_ids_.end());
   process_ids_[extension_id] = process_id;
 
   ExtensionsService* extension_service =