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The patch changes removes WTF type trais and changes the client code as following:
WTF::EnableIf -> std::enable_if
WTF::IsSameType -> std::is_same
WTF::IsConvertibleTo.. -> std::is_convertible
WTF::IsPolymorphic -> std::is_polymorphic

BUG=554293

Review URL: https://codereview.chromium.org/1477213003

Cr-Commit-Position: refs/heads/master@{#367242}