Make readBase64 an instance method

Leverage the existing code in File::read() and simply add in chunking and base64 encoding.

lib/Cake/Network/Email/CakeEmail.php

@@ -1385,7 +1385,8 @@ protected function _attachFiles($boundary = null) {
  * @return string File contents in base64 encoding
  */
 	protected function _readFile($file) {
-		return File::readAndBase64Encode($file);
+		$f = new File($file);
+		return $f->readBase64();
 	}
 
 /**

lib/Cake/Utility/File.php

@@ -181,18 +181,13 @@ public function read($bytes = false, $mode = 'rb', $force = false) {
 	}
 
 /**
- * Read the file contents and return a base64 version of the file contents.
+ * Return the contents of this File as a base64 version of the file contents.
  *
- * @param string $file The file to read.
  * @return string File contents in base64 encoding
  * @link http://book.cakephp.org/2.0/en/core-utility-libraries/file-folder.html#File::readAndBase64Encode
  */
-	public static function readAndBase64Encode($file) {
-		$handle = fopen($file, 'rb');
-		$data = fread($handle, filesize($file));
-		$data = chunk_split(base64_encode($data));
-		fclose($handle);
-		return $data;
+	public function readBase64() {
+		return chunk_split(base64_encode($this->read()));
 	}
 
 /**