code/Debug/Helper/Data.php
public function getLayoutUpdatesFiles($storeId, $designArea)
    {
        $updatesRoot = $this->getConfig()->getNode($designArea . '/layout/updates');

        // Find files with layout updates
        $updateFiles = array();

        /** @var Mage_Core_Model_Config_Element $updateNode */
        foreach ($updatesRoot->children() as $updateNode) {
            if ($updateNode->file) {
                $module = $updateNode->getAttribute('module');
                if ($module && Mage::getStoreConfigFlag('advanced/modules_disable_output/' . $module, $storeId)) {
                    continue;
                }
                $updateFiles[] = (string)$updateNode->file;
            }
        }
        // custom local layout updates file
        $updateFiles[] = 'local.xml';

        return $updateFiles;
    }
public function getLayoutUpdatesFiles($storeId, $designArea)
    {
        $updatesRoot = $this->getConfig()->getNode($designArea . '/layout/updates');

        // Find files with layout updates
        $updateFiles = array();

        /** @var Mage_Core_Model_Config_Element $updateNode */
        foreach ($updatesRoot->children() as $updateNode) {
            if ($updateNode->file) {
                $module = $updateNode->getAttribute('module');
                if ($module && Mage::getStoreConfigFlag('advanced/modules_disable_output/' . $module, $storeId)) {
                    continue;
                }
                $updateFiles[] = (string)$updateNode->file;
            }
        }
        // custom local layout updates file
        $updateFiles[] = 'local.xml';

        return $updateFiles;
    }
Returns all xml files that contains layout updates.

@param int    $storeId store identifier
@param string $designArea
@return array