struct UnloadedExtensionInfo -> enum UnloadedExtensionInfoReason

We don't need to keep struct UnloadedExtensionInfo.
So removing it and use enum UnloadedExtensionInfoReason instead.

TEST=Everything runs smoothly
BUG=715144

Review-Url: https://codereview.chromium.org/2839373003
Cr-Commit-Position: refs/heads/master@{#469065}
diff --git a/chrome/browser/extensions/tab_helper.h b/chrome/browser/extensions/tab_helper.h
index 5e81fba..09b09f6 100644
--- a/chrome/browser/extensions/tab_helper.h
+++ b/chrome/browser/extensions/tab_helper.h
@@ -152,7 +152,7 @@
   // ExtensionRegistryObserver:
   void OnExtensionUnloaded(content::BrowserContext* browser_context,
                            const Extension* extension,
-                           UnloadedExtensionInfo::Reason reason) override;
+                           UnloadedExtensionReason reason) override;
 
   // Message handlers.
   void OnDidGetWebApplicationInfo(const WebApplicationInfo& info);