Introduce runtime.onSuspendCanceled() event.

chrome/browser/extensions/extension_process_manager.cc

Index: chrome/browser/extensions/extension_process_manager.cc
diff --git a/chrome/browser/extensions/extension_process_manager.cc b/chrome/browser/extensions/extension_process_manager.cc
index ac453d6182d0aec5ae03f332171aeadcec37c91a..c847308cbf5f560a590fdc82427b93b48aed1f3f 100644
--- a/chrome/browser/extensions/extension_process_manager.cc
+++ b/chrome/browser/extensions/extension_process_manager.cc
@@ -112,9 +112,9 @@ struct ExtensionProcessManager::BackgroundPageData {
   int close_sequence_id;
 
   // True if the page responded to the ShouldUnload message and is currently
-  // dispatching the unload event. We use this to ignore any activity
-  // generated during the unload event that would otherwise keep the
-  // extension alive.
+  // dispatching the unload event. During this time any events that arrive will
+  // cancel the unload process and an onSuspendCanceled event will be dispatched
+  // to the page.
   bool is_closing;

[benwells, 2012/07/19 04:01:21]

Can we change this name too? 

[koz (OOO until 15th September), 2012/07/19 06:52:11]

See previous comment.

 
   // Keeps track of when this page was last unloaded. Used for perf metrics.
@@ -417,6 +417,7 @@ int ExtensionProcessManager::IncrementLazyKeepaliveCount(
   if (!extension->has_lazy_background_page())
     return 0;
 
+  background_page_data_[extension->id()].is_closing = false;
   int& count = background_page_data_[extension->id()].lazy_keepalive_count;
   if (++count == 1)
     OnLazyBackgroundPageActive(extension->id());
@@ -492,19 +493,24 @@ void ExtensionProcessManager::OnShouldUnloadAck(
 }
 
 void ExtensionProcessManager::OnUnloadAck(const std::string& extension_id) {
+  background_page_data_[extension_id].is_closing = true;
+  int sequence_id = background_page_data_[extension_id].close_sequence_id;
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&ExtensionProcessManager::CloseLazyBackgroundPageNow,
-                 weak_ptr_factory_.GetWeakPtr(), extension_id),
+                 weak_ptr_factory_.GetWeakPtr(), extension_id, sequence_id),
       event_page_unloading_time_);
 }
 
 void ExtensionProcessManager::CloseLazyBackgroundPageNow(
-    const std::string& extension_id) {
-  background_page_data_[extension_id].is_closing = true;
+    const std::string& extension_id, int sequence_id) {
   ExtensionHost* host = GetBackgroundHostForExtension(extension_id);
-  if (host)
-    CloseBackgroundHost(host);
+  if (host &&
+      sequence_id == background_page_data_[extension_id].close_sequence_id) {

[benwells, 2012/07/19 04:01:21]

Any change to sequence_id will cancel the unload. 

Is this the right set of events to cancel unload? I don't know what changes
sequence_id but it is probably more than an event being sent to the event page

A related question: can the unload be cancelled without the onSuspendCanceled
event being sent? It should not be possible.

[koz (OOO until 15th September), 2012/07/19 06:52:11]

Good point. I've changed it so that only dispatching an event can cause
onSuspendCancel().

+    ExtensionHost* host = GetBackgroundHostForExtension(extension_id);
+    if (host)
+      CloseBackgroundHost(host);
+  }
 }
 
 void ExtensionProcessManager::OnNetworkRequestStarted(