Index: wp-includes/vars.php
===================================================================
--- wp-includes/vars.php	(revision 15639)
+++ wp-includes/vars.php	(working copy)
@@ -41,7 +41,13 @@
 	if ( strpos($_SERVER['HTTP_USER_AGENT'], 'Lynx') !== false ) {
 		$is_lynx = true;
 	} elseif ( stripos($_SERVER['HTTP_USER_AGENT'], 'chrome') !== false ) {
-		$is_chrome = true;
+		if ( stripos( $_SERVER['HTTP_USER_AGENT'], 'chromeframe' ) !== false ) {
+			if ( $is_chrome = apply_filters( 'use_google_chrome_frame', is_admin() ) )
+				header( 'X-UA-Compatible: chrome=1' );
+			$is_winIE = ! $is_chrome;
+		} else {
+			$is_chrome = true;
+		}
 	} elseif ( stripos($_SERVER['HTTP_USER_AGENT'], 'safari') !== false ) {
 		$is_safari = true;
 	} elseif ( strpos($_SERVER['HTTP_USER_AGENT'], 'Gecko') !== false ) {