Revert "Remove obsolete float-management code from line layout"

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 751 matching lines @@
             'layout/line/InlineBox.cpp',
             'layout/line/InlineFlowBox.cpp',
             'layout/line/InlineIterator.h',
             'layout/line/InlineTextBox.cpp',
             'layout/line/LineBoxList.cpp',
             'layout/line/LineBreaker.cpp',
             'layout/line/LineBreaker.h',
             'layout/line/LineWidth.cpp',
             'layout/line/LineWidth.h',
             'layout/line/RootInlineBox.cpp',
+            'layout/line/TrailingFloatsRootInlineBox.h',
             'layout/line/TrailingObjects.cpp',
             'layout/line/TrailingObjects.h',
             'layout/shapes/BoxShape.cpp',
             'layout/shapes/BoxShape.h',
             'layout/shapes/PolygonShape.cpp',
             'layout/shapes/PolygonShape.h',
             'layout/shapes/RasterShape.cpp',
             'layout/shapes/RasterShape.h',
             'layout/shapes/RectangleShape.cpp',
             'layout/shapes/RectangleShape.h',
@@ skipping 3147 matching lines @@
             'style/ComputedStyleTest.cpp',
             'style/OutlineValueTest.cpp',
             'style/SVGComputedStyleTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }