Add a comma delimited syntax parser and use it for Accept-CH

Source/platform/blink_platform.gypi

 {
   'includes': [
     'platform_generated.gypi',
   ],
   'variables': {
     'platform_files': [
       'AsyncFileSystemCallbacks.h',
       'CalculationValue.h',
       'CheckedInt.h',
       'Clock.cpp',
       'Clock.h',
+      'CommaDelimitedParser.cpp',
+      'CommaDelimitedParser.h',
       'ContentDecryptionModuleResult.h',
       'ContentType.cpp',
       'ContentType.h',
       'ContextMenu.cpp',
       'ContextMenu.h',
       'ContextMenuItem.cpp',
       'ContextMenuItem.h',
       'Cookie.h',
       'CrossThreadCopier.cpp',
       'CrossThreadCopier.h',
@@ skipping 883 matching lines @@
       'weborigin/SecurityOriginCache.h',
       'weborigin/SecurityOriginHash.h',
       'weborigin/SecurityPolicy.cpp',
       'weborigin/SecurityPolicy.h',
       'win/HWndDC.h',
       'win/SystemInfo.cpp',
       'win/SystemInfo.h',
     ],
     'platform_test_files': [
       'ClockTest.cpp',
+      'CommaDelimitedParserTest.cpp',
       'DecimalTest.cpp',
       'DragImageTest.cpp',
       'LayoutUnitTest.cpp',
       'LifecycleContextTest.cpp',
       'PODArenaTest.cpp',
       'PODFreeListArenaTest.cpp',
       'PODIntervalTreeTest.cpp',
       'PODRedBlackTreeTest.cpp',
       'PurgeableVectorTest.cpp',
       'SharedBufferTest.cpp',
@@ skipping 61 matching lines @@
       'graphics/ImageLayerChromiumTest.cpp',
       'graphics/test/MockImageDecoder.h',
       'graphics/test/MockWebGraphicsContext3D.h',
       'image-decoders/bmp/BMPImageDecoderTest.cpp',
       'image-decoders/gif/GIFImageDecoderTest.cpp',
       'image-decoders/jpeg/JPEGImageDecoderTest.cpp',
       'image-decoders/webp/WEBPImageDecoderTest.cpp',
     ],
   },
 }