Remove GCC 4 workaround for DEFINE_STATIC_LOCAL

We no longer build with GCC 4 so this special casing can be removed.
After discussing this with Abarth, DEFINE_STATIC_LOCAL does have some
value on its own so I'm leaving that in for now.

R=abarth
BUG=263695

Review URL: https://chromiumcodereview.appspot.com/22266003

git-svn-id: svn://svn.chromium.org/blink/trunk@155551 bbb929c8-8fbe-4397-9dbb-9b2b20218538