Fix some clang warnings with -Wmissing-braces in base.

base/win/scoped_variant.cc

Index: base/win/scoped_variant.cc
diff --git a/base/win/scoped_variant.cc b/base/win/scoped_variant.cc
index f57ab93f6c66761b006b305223cad0b9139361d4..2cf265740d8b5f94a06866cbe375069e85991c50 100644
--- a/base/win/scoped_variant.cc
+++ b/base/win/scoped_variant.cc
@@ -9,7 +9,7 @@ namespace base {
 namespace win {
 
 // Global, const instance of an empty variant.
-const VARIANT ScopedVariant::kEmptyVariant = { VT_EMPTY };
+const VARIANT ScopedVariant::kEmptyVariant = {{{VT_EMPTY}}};
 
 ScopedVariant::~ScopedVariant() {
   COMPILE_ASSERT(sizeof(ScopedVariant) == sizeof(VARIANT), ScopedVariantSize);
@@ -82,7 +82,7 @@ VARIANT* ScopedVariant::Receive() {
 }
 
 VARIANT ScopedVariant::Copy() const {
-  VARIANT ret = { VT_EMPTY };
+  VARIANT ret = {{{VT_EMPTY}}};
   ::VariantCopy(&ret, &var_);
   return ret;
 }