Fix invalidating the text track indexes after append or remove text track from the list

third_party/WebKit/Source/core/html/track/TextTrackListTest.cpp

Index: third_party/WebKit/Source/core/html/track/TextTrackListTest.cpp
diff --git a/third_party/WebKit/Source/core/html/track/TextTrackListTest.cpp b/third_party/WebKit/Source/core/html/track/TextTrackListTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..8e312815fc5e6bd043ff7d6db99c7d9a7e960bf4
--- /dev/null
+++ b/third_party/WebKit/Source/core/html/track/TextTrackListTest.cpp
@@ -0,0 +1,38 @@
+// Copyright 2016 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.
+
+#include "core/html/track/TextTrackList.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace blink {
+
+TEST(TextTrackListTest, InvalidateTrackIndexes)
+{
+    // Create and fill the list
+    TextTrackList* list = TextTrackList::create(nullptr);
+    const size_t numTextTracks = 4;
+    TextTrack* textTracks[numTextTracks];
+    for (size_t i = 0; i < numTextTracks; ++i) {
+        textTracks[i] = TextTrack::create("subtitles", "", "");
+        list->append(textTracks[i]);
+    }
+
+    EXPECT_EQ(4u, list->length());
+    EXPECT_EQ(0, textTracks[0]->trackIndex());
+    EXPECT_EQ(1, textTracks[1]->trackIndex());
+    EXPECT_EQ(2, textTracks[2]->trackIndex());
+    EXPECT_EQ(3, textTracks[3]->trackIndex());
+
+    // Remove element from the middle of the list
+    list->remove(textTracks[1]);
+
+    EXPECT_EQ(3u, list->length());
+    EXPECT_EQ(nullptr, textTracks[1]->trackList());
+    EXPECT_EQ(0, textTracks[0]->trackIndex());
+    EXPECT_EQ(1, textTracks[2]->trackIndex());
+    EXPECT_EQ(2, textTracks[3]->trackIndex());
+}
+
+} // namespace blink