[Reland] Correct fixed-position recording for Slimming Paint

Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
@@ skipping 642 matching lines @@
       'graphics/paint/DisplayItemTransformTree.cpp',
       'graphics/paint/DisplayItemTransformTree.h',
       'graphics/paint/DisplayItemTransformTreeBuilder.cpp',
       'graphics/paint/DisplayItemTransformTreeBuilder.h',
       'graphics/paint/DrawingDisplayItem.cpp',
       'graphics/paint/DrawingDisplayItem.h',
       'graphics/paint/DrawingRecorder.cpp',
       'graphics/paint/DrawingRecorder.h',
       'graphics/paint/FilterDisplayItem.cpp',
       'graphics/paint/FilterDisplayItem.h',
+      'graphics/paint/FixedPositionContainerDisplayItem.cpp',
+      'graphics/paint/FixedPositionContainerDisplayItem.h',
+      'graphics/paint/FixedPositionDisplayItem.cpp',
+      'graphics/paint/FixedPositionDisplayItem.h',
       'graphics/paint/FloatClipDisplayItem.cpp',
       'graphics/paint/FloatClipDisplayItem.h',
       'graphics/paint/ScrollDisplayItem.cpp',
       'graphics/paint/ScrollDisplayItem.h',
       'graphics/paint/SkPictureRecorder.h',
       'graphics/paint/SubtreeDisplayItem.cpp',
       'graphics/paint/SubtreeDisplayItem.h',
       'graphics/paint/Transform3DDisplayItem.cpp',
       'graphics/paint/Transform3DDisplayItem.h',
       'graphics/paint/TransformDisplayItem.cpp',
@@ skipping 328 matching lines @@
       'image-decoders/webp/WEBPImageDecoderTest.cpp',
     ],
     'platform_unittest_support_files': [
       'testing/URLTestHelpers.cpp',
       'testing/URLTestHelpers.h',
       'testing/UnitTestHelpers.cpp',
       'testing/UnitTestHelpers.h',
     ],
   },
 }