Define Color::transparent et al. when using Clang on Windows
Define Color::transparent et al. when using Clang on Windows

MSVC treats their in-class initializations as definitions, but other
compilers don't. This updates the #ifdef to handle the Clang on Windows
case.

BUG=82385
TEST=build blink_web.dll with Clang on Windows in Release mode

Review URL: https://codereview.chromium.org/330823006

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@176469 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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