Change caching checks for minimized files

Only use a ETag, but include last modified time into this
Also added the filesize to this. And used the ETag for the
internal cache.

lib/minimizer.php

 <?php
 
 abstract class OC_Minimizer {
-	public function getLastModified($files) {
-		$last_modified = 0;
+	public function generateETag($files) {
+		$etag = '';
+		sort($files);
 		foreach($files as $file_info) {
 			$file = $file_info[0] . '/' . $file_info[2];
-			$filemtime = filemtime($file);
-			if ($filemtime > $last_modified) {
-				$last_modified = $filemtime;
-			}
+			$stat = stat($file);
+			$etag .= $file.$stat['mtime'].$stat['size'];
 		}
-		return $last_modified;
+		return md5($etag);
 	}
 
 	abstract public function minimizeFiles($files);
@@ -18,23 +17,21 @@ abstract class OC_Minimizer {
 	public function output($files, $cache_key) {
 		header('Content-Type: '.$this->contentType);
 		OC_Response::enableCaching();
-		$last_modified = $this->getLastModified($files);
-		OC_Response::setLastModifiedHeader($last_modified);
+		$etag = $this->generateETag($files);
+		$cache_key .= '-'.$etag;
 
 		$gzout = false;
 		$cache = OC_Cache::getGlobalCache();
 		if (!OC_Request::isNoCache() && (!defined('DEBUG') || !DEBUG)){
+			OC_Response::setETagHeader($etag);
 			$gzout = $cache->get($cache_key.'.gz');
-			if ($gzout) {
-				OC_Response::setETagHeader(md5($gzout));
-			}
 		}
 
 		if (!$gzout) {
 			$out = $this->minimizeFiles($files);
 			$gzout = gzencode($out);
-			OC_Response::setETagHeader(md5($gzout));
 			$cache->set($cache_key.'.gz', $gzout);
+			OC_Response::setETagHeader($etag);
 		}
 		if ($encoding = OC_Request::acceptGZip()) {
 			header('Content-Encoding: '.$encoding);
@@ -48,8 +45,8 @@ abstract class OC_Minimizer {
 
 	public function clearCache() {
 		$cache = OC_Cache::getGlobalCache();
-		$cache->delete('core.css.gz');
-		$cache->delete('core.js.gz');
+		$cache->clear('core.css');
+		$cache->clear('core.js');
 	}
 }