Deprecate direct use of legacy extension management preference

Use ExtensionManagement instead.

BUG=177351

Review URL: https://codereview.chromium.org/555323002

Cr-Commit-Position: refs/heads/master@{#294688}
diff --git a/chrome/browser/extensions/extension_management.h b/chrome/browser/extensions/extension_management.h
index 4aab9dd..1bfe39b 100644
--- a/chrome/browser/extensions/extension_management.h
+++ b/chrome/browser/extensions/extension_management.h
@@ -22,6 +22,7 @@
 #include "extensions/common/manifest.h"
 #include "extensions/common/url_pattern_set.h"
 
+class GURL;
 class PrefService;
 
 namespace content {
@@ -117,6 +118,9 @@
   // Returns if an extension with id |id| is allowed to install or not.
   bool IsInstallationAllowed(const ExtensionId& id) const;
 
+  // Returns true if an extension download should be allowed to proceed.
+  bool IsOffstoreInstallAllowed(const GURL& url, const GURL& referrer_url);
+
   // Helper function to read |settings_by_id_| with |id| as key. Returns a
   // constant reference to default settings if |id| does not exist.
   const IndividualSettings& ReadById(const ExtensionId& id) const;