Rename IntRectExtent to IntBoxExtent

Source/platform/blink_platform.gypi

 {
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.cpp',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
       'Clock.h',
       'ColorChooser.cpp',
@@ skipping 409 matching lines @@
       'geometry/FloatPoint3D.cpp',
       'geometry/FloatPoint3D.h',
       'geometry/FloatQuad.cpp',
       'geometry/FloatQuad.h',
       'geometry/FloatRect.cpp',
       'geometry/FloatRect.h',
       'geometry/FloatRoundedRect.cpp',
       'geometry/FloatRoundedRect.h',
       'geometry/FloatSize.cpp',
       'geometry/FloatSize.h',
+      'geometry/IntBoxExtent.h',
       'geometry/IntPoint.h',
       'geometry/IntRect.cpp',
       'geometry/IntRect.h',
-      'geometry/IntRectExtent.h',
       'geometry/IntSize.h',
       'geometry/IntSizeHash.h',
       'geometry/LayoutBoxExtent.cpp',
       'geometry/LayoutBoxExtent.h',
       'geometry/LayoutPoint.h',
       'geometry/LayoutRect.cpp',
       'geometry/LayoutRect.h',
       'geometry/LayoutSize.h',
       'geometry/Region.cpp',
       'geometry/Region.h',
@@ skipping 477 matching lines @@
       'graphics/ImageDecodingStoreTest.cpp',
       'graphics/ImageFrameGeneratorTest.cpp',
       'graphics/gpu/DrawingBufferTest.cpp',
       'graphics/test/MockImageDecoder.h',
       'graphics/test/MockWebGraphicsContext3D.h',
       'image-decoders/gif/GIFImageDecoderTest.cpp',
       'image-decoders/jpeg/JPEGImageDecoderTest.cpp',
     ],
   },
 }