Fixed EXIF parser bug.

BUG=chromium-os:25896
TEST=

Review URL: https://chromiumcodereview.appspot.com/9347020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@120781 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/file_manager/js/exif_parser.js

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -95,10 +95,8 @@ ExifParser.prototype.parseSlice = function(
 
       if (mark == EXIF_MARK_EXIF) {
         this.parseExifSection(metadata, buf, br);
-      } else if ((mark & ~0xF) == EXIF_MARK_SOF) {
+      } else if (ExifParser.isSOF_(mark)) {
         // The most reliable size information is encoded in the SOF section.
-        // There are 16 variants of the SOF format distinguished by the last
-        // hex digit of the mark, but the part we want is always the same.
         br.seek(1, ByteReader.SEEK_CUR); // Skip the precision byte.
         var height = br.readScalar(2);
         var width = br.readScalar(2);
@@ -114,6 +112,16 @@ ExifParser.prototype.parseSlice = function(
   }
 };
 
+ExifParser.isSOF_ = function(mark) {
+  // There are 13 variants of SOF fragment format distinguished by the last
+  // hex digit of the mark, but the part we want is always the same.
+  if ((mark & ~0xF) != EXIF_MARK_SOF) return false;
+
+  // If the last digit is 4, 8 or 12 it is not really a SOF.
+  var type = mark & 0xF;
+  return (type != 4 && type != 8 && type != 12);
+};
+
 ExifParser.prototype.parseExifSection = function(metadata, buf, br) {
   var magic = br.readString(6);
   if (magic != 'Exif\0\0') {