Fix bug where transient pages would miss events dispatched while it was

chrome/browser/extensions/extension_process_manager.h

Index: chrome/browser/extensions/extension_process_manager.h
diff --git a/chrome/browser/extensions/extension_process_manager.h b/chrome/browser/extensions/extension_process_manager.h
index c5a936ac6226646f41f2c2db4a5a46c03f732d71..eddf0cfa9571f9748cd0713f3bf448fbfdbae987 100644
--- a/chrome/browser/extensions/extension_process_manager.h
+++ b/chrome/browser/extensions/extension_process_manager.h
@@ -89,6 +89,10 @@ class ExtensionProcessManager : public content::NotificationObserver {
   // Returns true if |host| is managed by this process manager.
   bool HasExtensionHost(ExtensionHost* host) const;
 
+  // Returns true if the (lazy) background host for the given extension has
+  // already been sent the unload event and is shutting down.
+  bool IsBackgroundHostClosing(const std::string& extension_id);
+
   // Getter and setter for the lazy background page's keepalive count. This is
   // the count of how many outstanding "things" are keeping the page alive.
   // When this reaches 0, we will begin the process of shutting down the page.