Extensions: Remove workaround in SettingsOverrideAPIPermission::FromValue

The workaround was added due to a bug in Chrome versions before M46,
where we didn't persist the permission value in prefs (crbug.com/533086
and crbug.com/619759). By now, all users should long have updated prefs,
so time to get rid of the workaround.

Bug: none
Change-Id: I3c2581b96ece5b2a64db14f8d8df7ff93ff5cfc2
Reviewed-on: https://chromium-review.googlesource.com/1124688Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572225}

extensions/common/permissions/settings_override_permission.cc

@@ -50,14 +50,7 @@ bool SettingsOverrideAPIPermission::FromValue(
     const base::Value* value,
     std::string* /*error*/,
     std::vector<std::string>* unhandled_permissions) {
-  // Ugly hack: |value| being null should be an error. But before M46 beta, we
-  // didn't store the parameter for settings override permissions in prefs.
-  // See crbug.com/533086 and crbug.com/619759.
-  // TODO(treib,devlin): Remove this for M56, when hopefully all users will have
-  // updated prefs.
-  // This should read:
-  // return value && value->GetAsString(&setting_value_);
-  return !value || value->GetAsString(&setting_value_);
+  return value && value->GetAsString(&setting_value_);
 }
 
 std::unique_ptr<base::Value> SettingsOverrideAPIPermission::ToValue() const {