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/extensions/browser/extension_host.h b/extensions/browser/extension_host.h
index e40c384..fea09edc 100644
--- a/extensions/browser/extension_host.h
+++ b/extensions/browser/extension_host.h
@@ -131,7 +131,7 @@
                         const Extension* extension) override;
   void OnExtensionUnloaded(content::BrowserContext* browser_context,
                            const Extension* extension,
-                           UnloadedExtensionInfo::Reason reason) override;
+                           UnloadedExtensionReason reason) override;
 
  protected:
   // Called each time this ExtensionHost completes a load finishes loading,