namespace {} trick for SK_DECLARE_STATIC_ONCE

Like all our other SK_DECLARE_STATIC_*, it's usually not a thread-safe
thing to put inside a function.  Adding namespace {} prevents that
syntactically.

Needs https://codereview.chromium.org/841263004/ to land first.

BUG=chromium:447890

No public API changes.
TBR=reed@google.com

Review URL: https://codereview.chromium.org/806473006
diff --git a/src/utils/win/SkDWrite.cpp b/src/utils/win/SkDWrite.cpp
index 7801059..363ac43 100644
--- a/src/utils/win/SkDWrite.cpp
+++ b/src/utils/win/SkDWrite.cpp
@@ -41,10 +41,9 @@
 }
 
 
+SK_DECLARE_STATIC_ONCE(once);
 IDWriteFactory* sk_get_dwrite_factory() {
-    SK_DECLARE_STATIC_ONCE(once);
     SkOnce(&once, create_dwrite_factory, &gDWriteFactory);
-
     return gDWriteFactory;
 }