Introduce BorderImageLength and BorderImageLengthBox

Source/platform/blink_platform.gypi

 {
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.cpp',
       'CalculationValue.h',
       'Clock.cpp',
       'Clock.h',
       'ContentType.cpp',
       'ContentType.h',
@@ skipping 16 matching lines @@
       'JSONValues.h',
       'Language.cpp',
       'Language.h',
       'LayoutTestSupport.cpp',
       'LayoutTestSupport.h',
       'LayoutUnit.h',
       'Length.cpp',
       'Length.h',
       'LengthBox.cpp',
       'LengthBox.h',
+      'LengthBoxOrNumberBox.h',
       'LengthFunctions.cpp',
+      'LengthOrNumber.h',
       'LengthFunctions.h',
       'LengthPoint.h',
       'LengthSize.h',
       'LifecycleContext.h',
       'LifecycleNotifier.h',
       'LifecycleObserver.h',
       'LinkHash.cpp',
       'LinkHash.h',
       'Logging.cpp',
       'Logging.h',
@@ skipping 370 matching lines @@
       'geometry/RoundedRectTest.cpp',
       'graphics/ThreadSafeDataTransportTest.cpp',
       'testing/ArenaTestHelpers.h',
       'testing/TreeTestHelpers.cpp',
       'testing/TreeTestHelpers.h',
       'text/BidiResolverTest.cpp',
       'text/DateTimeFormatTest.cpp',
     ],
   },
 }