Use #if insteadof #ifdef DYNAMIC_ANNOTATIONS_ENABLED.  It's always defined, just to 0 or 1.

BUG=
R=mtklein

Review URL: https://codereview.chromium.org/26358010

git-svn-id: http://skia.googlecode.com/svn/trunk/src@11731 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/core/SkOnce.h b/core/SkOnce.h
index 26bf392..d5dd9d9 100644
--- a/core/SkOnce.h
+++ b/core/SkOnce.h
@@ -124,7 +124,7 @@
 // ANNOTATE_BENIGN_RACE, it might make sense to pull that in as a dependency
 // rather than continue to reproduce it here.
 
-#ifdef DYNAMIC_ANNOTATIONS_ENABLED
+#if DYNAMIC_ANNOTATIONS_ENABLED
 // TSAN provides this hook to supress a known-safe apparent race.
 extern "C" {
 void AnnotateBenignRace(const char* file, int line, const volatile void* mem, const char* desc);