Move text/BidiContext to Source/platform/

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSS.idl',
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSKeyframeRule.idl',
@@ skipping 3164 matching lines @@
             'platform/network/ResourceRequest.cpp',
             'platform/network/ResourceRequest.h',
             'platform/network/ResourceResponse.cpp',
             'platform/network/ResourceResponse.h',
             'platform/network/SocketStreamError.cpp',
             'platform/network/SocketStreamError.h',
             'platform/network/SocketStreamHandle.cpp',
             'platform/network/SocketStreamHandle.h',
             'platform/network/SocketStreamHandleClient.h',
             'platform/network/SocketStreamHandleInternal.h',
-            'platform/text/BidiContext.cpp',
             'platform/text/DateTimeFormat.cpp',
             'platform/text/LineEnding.cpp',
             'platform/text/LocaleICU.cpp',
             'platform/text/LocaleICU.h',
             'platform/text/LocaleToScriptMapping.h',
             'platform/text/LocaleToScriptMappingDefault.cpp',
             'platform/text/ParserUtilities.h',
             'platform/text/PlatformLocale.cpp',
             'platform/text/PlatformLocale.h',
             'platform/text/QuotedPrintable.h',
@@ skipping 645 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }