Paranoid temporary check that Chrome's building with SSE2 on all Windows builders.

BUG=chromium:475596

Review URL: https://codereview.chromium.org/1283183004
diff --git a/src/ports/SkGlobalInitialization_chromium.cpp b/src/ports/SkGlobalInitialization_chromium.cpp
index 3aecbd5..9568748 100644
--- a/src/ports/SkGlobalInitialization_chromium.cpp
+++ b/src/ports/SkGlobalInitialization_chromium.cpp
@@ -143,3 +143,7 @@
 void SkFlattenable::InitializeFlattenablesIfNeeded() {
     SkOnce(&once, SkPrivateEffectInitializer::Init);
 }
+
+#if defined(SK_BUILD_FOR_WIN32) && SK_CPU_SSE_LEVEL < SK_CPU_SSE_LEVEL_SSE2
+    #error "This double checks that Chromium is always built with SSE2+ on Windows."
+#endif