Introduce ForwardsTextBuffer and BackwardsTextBuffer

third_party/WebKit/Source/core/core.gypi

 {
     'includes': [
         'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/KeyframeEffect.idl',
             'animation/EffectModel.idl',
             'animation/AnimationEffectReadOnly.idl',
@@ skipping 1471 matching lines @@
             'editing/commands/TypingCommand.cpp',
             'editing/commands/TypingCommand.h',
             'editing/commands/UndoStack.cpp',
             'editing/commands/UndoStack.h',
             'editing/commands/UndoStep.h',
             'editing/commands/UnlinkCommand.cpp',
             'editing/commands/UnlinkCommand.h',
             'editing/commands/WrapContentsInDummySpanCommand.cpp',
             'editing/commands/WrapContentsInDummySpanCommand.h',
             'editing/iterators/BackwardsCharacterIterator.cpp',
+            'editing/iterators/BackwardsTextBuffer.cpp',
+            'editing/iterators/BackwardsTextBuffer.h',
             'editing/iterators/BitStack.cpp',
+            'editing/iterators/ForwardsTextBuffer.cpp',
+            'editing/iterators/ForwardsTextBuffer.h',
             'editing/iterators/FullyClippedStateStack.cpp',
             'editing/iterators/SearchBuffer.cpp',
             'editing/iterators/SearchBuffer.h',
+            'editing/iterators/TextBufferBase.cpp',
+            'editing/iterators/TextBufferBase.h',
             'editing/iterators/TextIterator.cpp',
             'editing/iterators/TextIterator.h',
             'editing/iterators/TextIteratorTextState.cpp',
             'editing/iterators/TextIteratorTextState.h',
             'editing/iterators/CharacterIterator.cpp',
             'editing/iterators/SimplifiedBackwardsTextIterator.cpp',
             'editing/iterators/WordAwareIterator.cpp',
             'editing/markers/DocumentMarker.cpp',
             'editing/markers/DocumentMarker.h',
             'editing/markers/DocumentMarkerController.cpp',
@@ skipping 2421 matching lines @@
             'dom/TreeScopeTest.cpp',
             'dom/URLSearchParamsTest.cpp',
             'dom/shadow/ComposedTreeTraversalTest.cpp',
             'editing/EditingStrategyTest.cpp',
             'editing/EditingTestBase.cpp',
             'editing/EditingTestBase.h',
             'editing/EditingUtilitiesTest.cpp',
             'editing/FrameSelectionTest.cpp',
             'editing/GranularityStrategyTest.cpp',
             'editing/InputMethodControllerTest.cpp',
+            'editing/iterators/BackwardsTextBufferTest.cpp',
             'editing/iterators/CharacterIteratorTest.cpp',
+            'editing/iterators/ForwardsTextBufferTest.cpp',
             'editing/iterators/SearchBufferTest.cpp',
             'editing/iterators/SimplifiedBackwardsTextIteratorTest.cpp',
             'editing/iterators/TextIteratorTest.cpp',
             'editing/markers/DocumentMarkerControllerTest.cpp',
             'editing/PositionTest.cpp',
             'editing/SelectionAdjusterTest.cpp',
             'editing/SurroundingTextTest.cpp',
             'editing/VisiblePositionTest.cpp',
             'editing/VisibleSelectionTest.cpp',
             'editing/VisibleUnitsTest.cpp',
@@ skipping 100 matching lines @@
             'style/SVGComputedStyleTest.cpp',
             'svg/SVGPathParserTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }