Remove DeferBackgroundExtensionCreation field trial and supporting code

chrome/browser/extensions/extension_system.cc

Index: chrome/browser/extensions/extension_system.cc
diff --git a/chrome/browser/extensions/extension_system.cc b/chrome/browser/extensions/extension_system.cc
index 377c9dafe227b23ba524b09d891d2a17679787f1..eda097970d190f849f0195d00c5e6d9a5541f8a7 100644
--- a/chrome/browser/extensions/extension_system.cc
+++ b/chrome/browser/extensions/extension_system.cc
@@ -337,9 +337,7 @@ void ExtensionSystemImpl::Shutdown() {
   process_manager_.reset();
 }
 
-void ExtensionSystemImpl::InitForRegularProfile(
-    bool extensions_enabled,
-    bool defer_background_creation) {
+void ExtensionSystemImpl::InitForRegularProfile(bool extensions_enabled) {
   DCHECK(!profile_->IsOffTheRecord());
   if (user_script_master() || extension_service())
     return;  // Already initialized.
@@ -349,9 +347,6 @@ void ExtensionSystemImpl::InitForRegularProfile(
 
   process_manager_.reset(ProcessManager::Create(profile_));
 
-  process_manager_->DeferBackgroundHostCreation(
-      defer_background_creation);
-
   shared_->Init(extensions_enabled);
 }