[LayoutNG] Add tests for ng_length_utils.

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/AnimationEffectReadOnly.idl',
             'animation/AnimationEffectTiming.idl',
@@ skipping 4204 matching lines @@
             'layout/MapCoordinatesTest.cpp',
             'layout/MultiColumnFragmentainerGroupTest.cpp',
             'layout/OverflowModelTest.cpp',
             'layout/PaginationTest.cpp',
             'layout/PaintContainmentTest.cpp',
             'layout/ScrollAnchorTest.cpp',
             'layout/TextAutosizerTest.cpp',
             'layout/VisualRectMappingTest.cpp',
             'layout/compositing/CompositedLayerMappingTest.cpp',
             'layout/ng/ng_block_layout_algorithm_test.cc',
+            'layout/ng/ng_length_utils_test.cc',
             'layout/shapes/BoxShapeTest.cpp',
             'layout/svg/LayoutSVGRootTest.cpp',
             'loader/DocumentLoadTimingTest.cpp',
             'loader/FrameFetchContextTest.cpp',
             'loader/LinkLoaderTest.cpp',
             'loader/MixedContentCheckerTest.cpp',
             'loader/TextResourceDecoderBuilderTest.cpp',
             'loader/ThreadableLoaderTest.cpp',
             'origin_trials/OriginTrialContextTest.cpp',
             'page/ChromeClientTest.cpp',
@@ skipping 31 matching lines @@
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'timing/PerformanceBaseTest.cpp',
             'timing/PerformanceObserverTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'workers/WorkerThreadTestHelper.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }