Index: src/wp-admin/admin.php
===================================================================
--- src/wp-admin/admin.php	(revision 25645)
+++ src/wp-admin/admin.php	(working copy)
@@ -36,15 +36,22 @@
 	update_option( 'db_upgraded',  false );
 
 	/**
-	 * Runs on the next page load after successful upgrade
+	 * Fires on the next page load after successful upgrade
 	 *
 	 * @since 2.8
 	 */
-	do_action('after_db_upgrade');
+	do_action( 'after_db_upgrade' );
 } elseif ( get_option('db_version') != $wp_db_version && empty($_POST) ) {
 	if ( !is_multisite() ) {
 		wp_redirect( admin_url( 'upgrade.php?_wp_http_referer=' . urlencode( wp_unslash( $_SERVER['REQUEST_URI'] ) ) ) );
 		exit;
+	/**
+	 * Filter whether to perform the Multisite upgrade routine.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param bool true Whether to perform the Multisite upgrade routine. Default true.
+	 */
 	} elseif ( apply_filters( 'do_mu_upgrade', true ) ) {
 		/**
 		 * On really small MU installs run the upgrader every time,
@@ -57,6 +64,13 @@
 		if ( $c <= 50 || ( $c > 50 && mt_rand( 0, (int)( $c / 50 ) ) == 1 ) ) {
 			require_once( ABSPATH . WPINC . '/http.php' );
 			$response = wp_remote_get( admin_url( 'upgrade.php?step=1' ), array( 'timeout' => 120, 'httpversion' => '1.1' ) );
+			/**
+			 * Fires after the Multisite upgrade is complete.
+			 *
+			 * @since 3.0.0
+			 *
+			 * @param array|WP_Error $response The upgrade response array or WP_Error on failure.
+			 */
 			do_action( 'after_mu_upgrade', $response );
 			unset($response);
 		}
@@ -103,10 +117,26 @@
 else
 	require(ABSPATH . 'wp-admin/menu.php');
 
-if ( current_user_can( 'manage_options' ) )
+if ( current_user_can( 'manage_options' ) ) {
+	/**
+	 * Filter the maximum memory limit available for administration screens.
+	 *
+	 * The WP_MAX_MEMORY_LIMIT constant specifically defines the maximum memory limit available
+	 * when in the administration back-end. The default is 256M, or 256 megabytes of memory.
+	 *
+	 * @since 3.0.0
+	 *
+	 * @param string 'WP_MAX_MEMORY_LIMIT' The maximum WordPress memory limit. Default 256M.
+	 */
 	@ini_set( 'memory_limit', apply_filters( 'admin_memory_limit', WP_MAX_MEMORY_LIMIT ) );
+}
 
-do_action('admin_init');
+/**
+ * Fires at the beginning of any admin page, before the page is rendered.
+ *
+ * @since 2.5.0
+ */
+do_action( 'admin_init' );
 
 if ( isset($plugin_page) ) {
 	if ( !empty($typenow) )
@@ -142,11 +172,42 @@
 // Handle plugin admin pages.
 if ( isset($plugin_page) ) {
 	if ( $page_hook ) {
-		do_action('load-' . $page_hook);
+		/**
+		 * Fires before a plugin page is loaded where $page_hook is not empty.
+		 *
+		 * The dynamic portion of the hook name, $page_hook, refers to a mixture of plugin
+		 * page information including:
+		 * 1. The page type. If the plugin page is registered as a submenu page,
+		 *    such as for Settings, the page type would be 'settings'. Otherwise the type is 'toplevel'.
+		 * 2. A separator of '_page_'.
+		 * 3. The plugin basename minus the file extension.
+		 *
+		 * Together, the three parts form the $page_hook. Citing the example
+		 * above, the hook name used would be 'load-settings_page_pluginbasename'.
+		 *
+		 * @see get_plugin_page_hook()
+		 *
+		 * @since 2.1.0
+		 */
+		do_action( 'load-' . $page_hook );
 		if (! isset($_GET['noheader']))
 			require_once(ABSPATH . 'wp-admin/admin-header.php');
 
-		do_action($page_hook);
+		/**
+		 * Fires after the admin header is loaded for a plugin page where $page_hook is not empty.
+		 *
+		 * The dynamic hook name, $page_hook, refers to a mixture of plugin page information including:
+		 * 1. The page type. If the plugin page is registered as a submenu page,
+		 *    such as for Settings, the page type would be 'settings'. Otherwise the type is 'toplevel'.
+		 * 2. A separator of '_page_'.
+		 * 3. The plugin basename minus the file extension.
+		 *
+		 * Together, the three parts form the $page_hook. Citing the example
+		 * above, the hook name used would be 'load-settings_page_pluginbasename'.
+		 *
+		 * @since 1.5.0
+		 */
+		do_action( $page_hook );
 	} else {
 		if ( validate_file($plugin_page) )
 			wp_die(__('Invalid plugin page'));
@@ -154,7 +215,16 @@
 		if ( !( file_exists(WP_PLUGIN_DIR . "/$plugin_page") && is_file(WP_PLUGIN_DIR . "/$plugin_page") ) && !( file_exists(WPMU_PLUGIN_DIR . "/$plugin_page") && is_file(WPMU_PLUGIN_DIR . "/$plugin_page") ) )
 			wp_die(sprintf(__('Cannot load %s.'), htmlentities($plugin_page)));
 
-		do_action('load-' . $plugin_page);
+		/**
+		 * Fires before a plugin page is loaded where $page_hook is empty.
+		 *
+		 * The dynamic portion of the hook name, $plugin_page, refers to the plugin basename.
+		 *
+		 * @see plugin_basename()
+		 *
+		 * @since 1.5.0
+		 */
+		do_action( 'load-' . $plugin_page );
 
 		if ( !isset($_GET['noheader']))
 			require_once(ABSPATH . 'wp-admin/admin-header.php');
@@ -185,6 +255,13 @@
 		exit;
 	}
 
+	/**
+	 * Fires before an importer page is loaded.
+	 *
+	 * The dynamic portion of the hook name, $importer, refers to the importer slug.
+	 *
+	 * @since 3.5.0
+	 */
 	do_action( 'load-importer-' . $importer );
 
 	$parent_file = 'tools.php';
@@ -198,6 +275,16 @@
 
 	define('WP_IMPORTING', true);
 
+	/**
+	 * Whether to filter imported data through kses on import.
+	 *
+	 * In Multisite, imported data is filtered through kses by default
+	 * by filtering on this hook and returning true.
+	 *
+	 * @since 3.1.0
+	 *
+	 * @param bool false Whether to force data to be filtered through kses. Default false.
+	 */
 	if ( apply_filters( 'force_filtered_html_on_import', false ) )
 		kses_init_filters();  // Always filter imported data with kses on multisite.
 
@@ -210,7 +297,16 @@
 
 	exit();
 } else {
-	do_action("load-$pagenow");
+	/**
+	 * Fires before an admin page is loaded.
+	 *
+	 * The dynamic portion of the hook name, $pagenow, is a global variable
+	 * referring to the filename of the current page, such as 'admin.php',
+	 * 'post-new.php' etc. A complete hook for the latter would be 'load-post-new.php'.
+	 *
+	 * @since 2.1.0
+	 */
+	do_action( 'load-' . $pagenow );
 	// Backwards compatibility with old load-page-new.php, load-page.php,
 	// and load-categories.php actions.
 	if ( $typenow == 'page' ) {
@@ -226,5 +322,14 @@
 	}
 }
 
-if ( !empty($_REQUEST['action']) )
+if ( !empty($_REQUEST['action']) ) {
+	/**
+	 * Fires before the page loads for the requested action.
+	 *
+	 * The dynamic portion of the hook name, $_REQUEST['action'], refers to the action
+	 * derived from the $_REQUEST super global passed to admin.php.
+	 *
+	 * @since 2.6.0
+	 */
 	do_action('admin_action_' . $_REQUEST['action']);
+}