Move RenderBlockFlow::constructTextRun out.

Source/core/core.gypi

 {
     'includes': [
       'core_generated.gypi',
     ],
     'variables': {
         # Files for which bindings (.cpp and .h files) will be generated
         'core_idl_files': [
             'animation/Animation.idl',
             'animation/AnimationEffect.idl',
             'animation/AnimationPlayer.idl',
@@ skipping 1658 matching lines @@
             'rendering/RenderWidget.cpp',
             'rendering/RenderWordBreak.cpp',
             'rendering/RenderWordBreak.h',
             'rendering/RootInlineBox.cpp',
             'rendering/ScrollAlignment.cpp',
             'rendering/SubtreeLayoutScope.cpp',
             'rendering/SubtreeLayoutScope.h',
             'rendering/TableLayout.h',
             'rendering/TextAutosizer.cpp',
             'rendering/TextAutosizer.h',
+            'rendering/TextRunConstructor.cpp',
+            'rendering/TextRunConstructor.h',
             'rendering/TrailingFloatsRootInlineBox.h',
             'rendering/VerticalPositionCache.h',
             'rendering/break_lines.cpp',
             'rendering/break_lines.h',
             'rendering/compositing/CompositedLayerMapping.cpp',
             'rendering/compositing/CompositedLayerMapping.h',
             'rendering/compositing/CompositedLayerMappingPtr.h',
             'rendering/compositing/CompositingInputsUpdater.cpp',
             'rendering/compositing/CompositingInputsUpdater.h',
             'rendering/compositing/CompositingLayerAssigner.cpp',
@@ skipping 1726 matching lines @@
             'rendering/RenderOverflowTest.cpp',
             'rendering/RenderTableCellTest.cpp',
             'rendering/RenderTableRowTest.cpp',
             'rendering/shapes/BoxShapeTest.cpp',
             'testing/UnitTestHelpers.cpp',
             'testing/UnitTestHelpers.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }