Extract ProcessManager from ExtensionSystem.

chrome/browser/extensions/alert_apitest.cc

Index: chrome/browser/extensions/alert_apitest.cc
diff --git a/chrome/browser/extensions/alert_apitest.cc b/chrome/browser/extensions/alert_apitest.cc
index dbd7c5569e3f57e8679d844468baf9f0d906ed89..2b5787408ac8de7c534cc6383b304003a9c9333e 100644
--- a/chrome/browser/extensions/alert_apitest.cc
+++ b/chrome/browser/extensions/alert_apitest.cc
@@ -10,7 +10,6 @@
 #include "components/app_modal_dialogs/app_modal_dialog.h"
 #include "content/public/browser/render_frame_host.h"
 #include "extensions/browser/extension_host.h"
-#include "extensions/browser/extension_system.h"
 #include "extensions/browser/process_manager.h"
 #include "extensions/common/extension.h"
 
@@ -19,8 +18,8 @@ IN_PROC_BROWSER_TEST_F(ExtensionApiTest, AlertBasic) {
 
   const extensions::Extension* extension = GetSingleLoadedExtension();
   extensions::ExtensionHost* host =
-      extensions::ExtensionSystem::Get(browser()->profile())->
-          process_manager()->GetBackgroundHostForExtension(extension->id());
+      extensions::ProcessManager::Get(browser()->profile())
+          ->GetBackgroundHostForExtension(extension->id());
   ASSERT_TRUE(host);
   host->host_contents()->GetMainFrame()->ExecuteJavaScript(
       base::ASCIIToUTF16("alert('This should not crash.');"));