Take extensions out of Profile into a profile-keyed service, ExtensionSystem.

chrome/browser/extensions/extension_devtools_bridge.cc

Index: chrome/browser/extensions/extension_devtools_bridge.cc
diff --git a/chrome/browser/extensions/extension_devtools_bridge.cc b/chrome/browser/extensions/extension_devtools_bridge.cc
index e31767f2d5efa85afa25fb168a7aa5e4f60c1cbf..22f72b30fd693fe2920f044bd37db09af3cc9042 100644
--- a/chrome/browser/extensions/extension_devtools_bridge.cc
+++ b/chrome/browser/extensions/extension_devtools_bridge.cc
@@ -12,6 +12,8 @@
 #include "chrome/browser/extensions/extension_devtools_events.h"
 #include "chrome/browser/extensions/extension_devtools_manager.h"
 #include "chrome/browser/extensions/extension_event_router.h"
+#include "chrome/browser/extensions/extension_system.h"
+#include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/extensions/extension_tab_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
@@ -32,7 +34,8 @@ ExtensionDevToolsBridge::ExtensionDevToolsBridge(int tab_id,
           ExtensionDevToolsEvents::OnPageEventNameForTab(tab_id)),
       on_tab_close_event_name_(
           ExtensionDevToolsEvents::OnTabCloseEventNameForTab(tab_id)) {
-  extension_devtools_manager_ = profile_->GetExtensionDevToolsManager();
+  extension_devtools_manager_ =
+      ExtensionSystemFactory::GetForProfile(profile)->devtools_manager();
   DCHECK(extension_devtools_manager_.get());
 }