Handle buffer boundaries in the WebVTT parser

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSKeyframeRule.idl',
@@ skipping 2604 matching lines @@
             'html/shadow/SliderThumbElement.cpp',
             'html/shadow/SliderThumbElement.h',
             'html/shadow/SpinButtonElement.cpp',
             'html/shadow/SpinButtonElement.h',
             'html/shadow/TextControlInnerElements.cpp',
             'html/shadow/TextControlInnerElements.h',
             'html/ime/Composition.cpp',
             'html/ime/Composition.h',
             'html/ime/InputMethodContext.cpp',
             'html/ime/InputMethodContext.h',
+            'html/track/BufferedLineReader.cpp',
+            'html/track/BufferedLineReader.h',
             'html/track/InbandTextTrack.cpp',
             'html/track/InbandTextTrack.h',
             'html/track/LoadableTextTrack.cpp',
             'html/track/LoadableTextTrack.h',
             'html/track/TextTrack.cpp',
             'html/track/TextTrack.h',
             'html/track/TextTrackCue.cpp',
             'html/track/TextTrackCue.h',
             'html/track/TextTrackCueList.cpp',
             'html/track/TextTrackCueList.h',
@@ skipping 876 matching lines @@
             'animation/TimedItemTest.cpp',
             'css/CSSParserValuesTest.cpp',
             'css/CSSCalculationValueTest.cpp',
             'css/CSSValueTestHelper.h',
             'fetch/ImageResourceTest.cpp',
             'fetch/MemoryCacheTest.cpp',
             'fetch/ResourceFetcherTest.cpp',
             'html/HTMLDimensionTest.cpp',
             'html/LinkRelAttributeTest.cpp',
             'html/TimeRangesTest.cpp',
+            'html/track/BufferedLineReaderTest.cpp',
             'frame/ImageBitmapTest.cpp',
             'platform/animation/AnimationTranslationUtilTest.cpp',
             'platform/animation/TimingFunctionTestHelper.h',
             'platform/animation/TimingFunctionTestHelper.cpp',
             'platform/animation/TimingFunctionTestHelperTest.cpp',
             'platform/graphics/BitmapImageTest.cpp',
             'platform/graphics/FontTest.cpp',
             'platform/graphics/GraphicsContextTest.cpp',
             'platform/graphics/chromium/Canvas2DLayerBridgeTest.cpp',
             'platform/graphics/chromium/Canvas2DLayerManagerTest.cpp',
             'platform/graphics/chromium/DeferredImageDecoderTest.cpp',
             'platform/graphics/chromium/ImageDecodingStoreTest.cpp',
             'platform/graphics/chromium/ImageFrameGeneratorTest.cpp',
             'platform/graphics/chromium/test/MockDiscardablePixelRef.h',
             'platform/graphics/chromium/test/MockImageDecoder.h',
             'platform/graphics/gpu/DrawingBufferTest.cpp',
             'platform/image-decoders/ImageDecoderTest.cpp',
             'platform/image-decoders/gif/GIFImageDecoderTest.cpp',
             'platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp',
             'platform/image-decoders/webp/WEBPImageDecoderTest.cpp',
             'platform/testing/FakeWebGraphicsContext3D.h',
             'rendering/RenderOverflowTest.cpp',
         ],
     }
 }