Add note about Chromium's use of old libstdc++ to docs.

Chromium must still build against libstdc++4.6.4, which presents limits
on at least type traits and perhaps performance.

NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=1820873002

Review URL: https://codereview.chromium.org/1820873002

diff --git a/site/dev/contrib/c++11.md b/site/dev/contrib/c++11.md
index 1854feb3b60b2c430c4e522d2a451e8f6393e521..432ad88f3a80689533927ab744d620dcd1ef4e27 100644 (file)
--- a/site/dev/contrib/c++11.md
+++ b/site/dev/contrib/c++11.md
@@ -24,7 +24,9 @@ internal Google projects.
 
 Chrome builds with a recent Clang on Mac and Linux and with a recent MSVC on
 Windows.  These toolchains are new enough to not be the weak link to use any
-C++11 language feature.
+C++11 language feature.  Chromium, however, builds against libstdc++4.6.4
+(STL and runtime) on Linux.  This precludes direct use of a number of type
+traits.
 
 Chrome intentionally disables thread-safe initialization of static variables,
 so we cannot rely on that.  Our bots disable this too, so keep an eye on TSAN.