This change allows linter standards to be reused with different linters. For example, you can define a PSR-2 linter standard which applies to ArcanistTextLinter and ArcanistXHPASTLinter.
public function getLinterConfiguration(ArcanistLinter $linter) { if ($linter instanceof ArcanistTextLinter) { return array( // ... ); } else if ($linter instanceof ArcanistXHPASTLinter) { return array( // ... ); } }