[Extensions] Ensure ordering of extension [un]loaded, activated messages

extensions/renderer/dispatcher.cc

Index: extensions/renderer/dispatcher.cc
diff --git a/extensions/renderer/dispatcher.cc b/extensions/renderer/dispatcher.cc
index df6e9cd4aa1ce3853b575e82d99ced795d8c007f..bfcbcf2b3d2648ba7818c441d5264dbfa57454c3 100644
--- a/extensions/renderer/dispatcher.cc
+++ b/extensions/renderer/dispatcher.cc
@@ -996,6 +996,7 @@ void Dispatcher::OnActivateExtension(const std::string& extension_id) {
   const Extension* extension =
       RendererExtensionRegistry::Get()->GetByID(extension_id);
   if (!extension) {
+    NOTREACHED();
     // Extension was activated but was never loaded. This probably means that
     // the renderer failed to load it (or the browser failed to tell us when it
     // did). Failures shouldn't happen, but instead of crashing there (which
@@ -1091,8 +1092,11 @@ void Dispatcher::OnLoaded(
     //    Dispatcher is attached to a RenderThread. Presumably there is a
     //    mismatch there. In theory one would think it's possible for the
     //    browser to figure this out itself - but again, cost/benefit.
-    if (!extension_registry->Contains(extension->id()))
-      extension_registry->Insert(extension);
+    if (!extension_registry->Insert(extension)) {
+      // TODO(devlin): This may be fixed by crbug.com/528026. Monitor, and
+      // consider making this a release CHECK.
+      NOTREACHED();
+    }
   }
 
   // Update the available bindings for all contexts. These may have changed if
@@ -1154,8 +1158,12 @@ void Dispatcher::OnTransferBlobs(const std::vector<std::string>& blob_uuids) {
 void Dispatcher::OnUnloaded(const std::string& id) {
   // See comment in OnLoaded for why it would be nice, but perhaps incorrect,
   // to CHECK here rather than guarding.
-  if (!RendererExtensionRegistry::Get()->Remove(id))
+  // TODO(devlin): This may be fixed by crbug.com/528026. Monitor, and
+  // consider making this a release CHECK.
+  if (!RendererExtensionRegistry::Get()->Remove(id)) {
+    NOTREACHED();
     return;
+  }
 
   active_extension_ids_.erase(id);