Don't use 'defined' in macro expansion.

Don't use 'defined' in macro expansion.

A careful reading of the preprocessor specification indicates that
any use of the 'defined' operator outside the form of 'defined X' or
'defined ( X )' directly in the constant expression of a '#if' or
'#elif' may cause undefined behavior.

In particular, msvc is very unpredictable. The 'defined X' and
'defined ( X )' forms behave differently when created from marco
expansion, with 'defined ( X )' generally evaluating to '0L'. The
'defined X' form generally behaves more the way one would expect,
but still has a number of quirks which should simply be considered
undefined behavior.

BUG=chromium:419245
Committed: https://skia.googlesource.com/skia/+/8dfdfff98dd14b0f3bef465411941e1bab8f0261

[bungeman-skia, 2014-10-15 19:51:16]

bungeman@google.com changed reviewers:
+ mtklein@google.com, reed@google.com

[mtklein, 2014-10-15 19:52:40]

lgtm

[reed1, 2014-10-15 20:42:21]

lgtm

[bungeman-skia, 2014-10-15 20:42:58]

The CQ bit was checked by bungeman@google.com

[commit-bot: I haz the power, 2014-10-15 20:44:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/657183002/1

[commit-bot: I haz the power, 2014-10-15 20:54:05]

Committed patchset #1 (id:1) as 8dfdfff98dd14b0f3bef465411941e1bab8f0261