Add methods for creating V8 extras-based ReadableStreams from C++

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 245 matching lines @@
             'inspector/InspectorOverlayHost.idl',
             'loader/appcache/ApplicationCache.idl',
             'page/EventSource.idl',
             'page/PagePopupController.idl',
             'page/scrolling/ScrollState.idl',
             'page/scrolling/ScrollStateCallback.idl',
             'streams/ReadableByteStream.idl',
             'streams/ReadableByteStreamReader.idl',
             'streams/ReadableStreamReader.idl',
             'streams/Stream.idl',
+            'streams/UnderlyingSourceBase.idl',
             'svg/SVGAElement.idl',
             'svg/SVGAngle.idl',
             'svg/SVGAnimateElement.idl',
             'svg/SVGAnimateMotionElement.idl',
             'svg/SVGAnimateTransformElement.idl',
             'svg/SVGAnimatedAngle.idl',
             'svg/SVGAnimatedBoolean.idl',
             'svg/SVGAnimatedEnumeration.idl',
             'svg/SVGAnimatedInteger.idl',
             'svg/SVGAnimatedLength.idl',
@@ skipping 1866 matching lines @@
             'streams/ReadableByteStream.h',
             'streams/ReadableByteStreamReader.h',
             'streams/ReadableStream.cpp',
             'streams/ReadableStream.h',
             'streams/ReadableStreamImpl.h',
             'streams/ReadableStreamReader.cpp',
             'streams/ReadableStreamReader.h',
             'streams/Stream.cpp',
             'streams/Stream.h',
             'streams/UnderlyingSource.h',
+            'streams/UnderlyingSourceBase.h',
+            'streams/UnderlyingSourceBase.cpp',
             'timing/ConsoleMemory.cpp',
             'timing/ConsoleMemory.h',
             'timing/DOMWindowPerformance.cpp',
             'timing/DOMWindowPerformance.h',
             'timing/MemoryInfo.cpp',
             'timing/Performance.cpp',
             'timing/Performance.h',
             'timing/PerformanceBase.cpp',
             'timing/PerformanceBase.h',
             'timing/PerformanceCompositeTiming.cpp',
@@ skipping 1873 matching lines @@
             'style/SVGComputedStyleTest.cpp',
             'svg/SVGPathParserTest.cpp',
             'svg/UnsafeSVGAttributeSanitizationTest.cpp',
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }