Simplify subtree (now subsequence) caching

Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
@@ skipping 662 matching lines @@
       '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/SkPictureBuilder.h',
-      'graphics/paint/SubtreeDisplayItem.h',
-      'graphics/paint/SubtreeRecorder.cpp',
-      'graphics/paint/SubtreeRecorder.h',
+      'graphics/paint/SubsequenceDisplayItem.h',
+      'graphics/paint/SubsequenceRecorder.cpp',
+      'graphics/paint/SubsequenceRecorder.h',
       'graphics/paint/Transform3DDisplayItem.cpp',
       'graphics/paint/Transform3DDisplayItem.h',
       'graphics/paint/TransformDisplayItem.cpp',
       'graphics/paint/TransformDisplayItem.h',
       'graphics/paint/CompositingDisplayItem.cpp',
       'graphics/paint/CompositingDisplayItem.h',
       'graphics/skia/SkSizeHash.h',
       'graphics/skia/SkiaUtils.cpp',
       'graphics/skia/SkiaUtils.h',
       'image-decoders/FastSharedBufferReader.cpp',
@@ skipping 363 matching lines @@
       ['os_posix==1 and OS!="mac"',
         {
           'platform_test_files': [
             'text/LocaleICUTest.cpp',
           ],
         }
       ],
     ],
   },
 }