First version of new merge algorithm (not enabled yet)

Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
@@ skipping 638 matching lines @@
       '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/FloatClipDisplayItem.cpp',
       'graphics/paint/FloatClipDisplayItem.h',
       'graphics/paint/ScrollDisplayItem.cpp',
       'graphics/paint/ScrollDisplayItem.h',
+      'graphics/paint/SubtreeDisplayItem.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/GaneshUtils.cpp',
       'graphics/skia/GaneshUtils.h',
       'graphics/skia/NativeImageSkia.cpp',
       'graphics/skia/NativeImageSkia.h',
@@ skipping 311 matching lines @@
       'graphics/ImageFrameGeneratorTest.cpp',
       'graphics/ImageLayerChromiumTest.cpp',
       'graphics/test/MockImageDecoder.h',
       'graphics/test/MockWebGraphicsContext3D.h',
       'image-decoders/gif/GIFImageDecoderTest.cpp',
       'image-decoders/jpeg/JPEGImageDecoderTest.cpp',
       'image-decoders/webp/WEBPImageDecoderTest.cpp',
     ],
   },
 }