Optimize the content type search.

Move most commonly used types to the top
of the list.  This reduces the time spent
iterating content types.

lib/Cake/Network/CakeResponse.php

@@ -80,6 +80,10 @@ class CakeResponse {
  * @var array
  */
 	protected $_mimeTypes = array(
+		'html' => array('text/html', '*/*'),
+		'json' => 'application/json',
+		'xml' => array('application/xml', 'text/xml'),
+		'rss' => 'application/rss+xml',
 		'ai' => 'application/postscript',
 		'bcpio' => 'application/x-bcpio',
 		'bin' => 'application/octet-stream',
@@ -206,7 +210,6 @@ class CakeResponse {
 		'f90' => 'text/plain',
 		'h' => 'text/plain',
 		'hh' => 'text/plain',
-		'html' => array('text/html', '*/*'),
 		'htm' => array('text/html', '*/*'),
 		'ics' => 'text/calendar',
 		'm' => 'text/plain',
@@ -218,7 +221,6 @@ class CakeResponse {
 		'tpl' => 'text/template',
 		'txt' => 'text/plain',
 		'text' => 'text/plain',
-		'xml' => array('application/xml', 'text/xml'),
 		'avi' => 'video/x-msvideo',
 		'fli' => 'video/x-fli',
 		'mov' => 'video/quicktime',
@@ -261,12 +263,10 @@ class CakeResponse {
 		'pdb' => 'chemical/x-pdb',
 		'xyz' => 'chemical/x-pdb',
 		'javascript' => 'text/javascript',
-		'json' => 'application/json',
 		'form' => 'application/x-www-form-urlencoded',
 		'file' => 'multipart/form-data',
 		'xhtml'	=> array('application/xhtml+xml', 'application/xhtml', 'text/xhtml'),
 		'xhtml-mobile'	=> 'application/vnd.wap.xhtml+xml',
-		'rss' => 'application/rss+xml',
 		'atom' => 'application/atom+xml',
 		'amf' => 'application/x-amf',
 		'wap' => array('text/vnd.wap.wml', 'text/vnd.wap.wmlscript', 'image/vnd.wap.wbmp'),