SameSite: Correctly set requests' initiator for new tabs.

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 1903 matching lines @@
             'loader/DocumentLoader.cpp',
             'loader/DocumentThreadableLoader.cpp',
             'loader/DocumentThreadableLoader.h',
             'loader/DocumentThreadableLoaderClient.h',
             'loader/DocumentWriter.cpp',
             'loader/EmptyClients.cpp',
             'loader/EmptyClients.h',
             'loader/FormSubmission.cpp',
             'loader/FrameFetchContext.cpp',
             'loader/FrameFetchContext.h',
+            'loader/FrameLoadRequest.cpp',
             'loader/FrameLoadRequest.h',
             'loader/FrameLoader.cpp',
             'loader/FrameLoaderStateMachine.cpp',
             'loader/HistoryItem.cpp',
             'loader/HistoryItem.h',
             'loader/HttpEquiv.cpp',
             'loader/HttpEquiv.h',
             'loader/ImageLoader.cpp',
             'loader/ImageLoader.h',
             'loader/LinkLoader.cpp',
@@ skipping 2254 matching lines @@
             'testing/PrivateScriptTestTest.cpp',
             'timing/MemoryInfoTest.cpp',
             'timing/PerformanceBaseTest.cpp',
             'timing/PerformanceObserverTest.cpp',
             'workers/WorkerThreadTest.cpp',
             'workers/WorkerThreadTestHelper.h',
             'xml/parser/SharedBufferReaderTest.cpp',
         ],
     }
 }