Ensure only whitelisted stubs have sse2 versions in the snapshot.

src/assembler.cc

Index: src/assembler.cc
diff --git a/src/assembler.cc b/src/assembler.cc
index 6581aa1305a459fdc8c90b31d0a9faabf9f78169..cd2bedd4287ea40655c12f56a5442e51c198d826 100644
--- a/src/assembler.cc
+++ b/src/assembler.cc
@@ -210,19 +210,14 @@ CpuFeatureScope::~CpuFeatureScope() {
 // Implementation of PlatformFeatureScope
 
 PlatformFeatureScope::PlatformFeatureScope(CpuFeature f)
-    : old_supported_(CpuFeatures::supported_),
-      old_found_by_runtime_probing_only_(
-          CpuFeatures::found_by_runtime_probing_only_) {
+    : old_cross_compile_(CpuFeatures::cross_compile_) {
   uint64_t mask = static_cast<uint64_t>(1) << f;
-  CpuFeatures::supported_ |= mask;
-  CpuFeatures::found_by_runtime_probing_only_ &= ~mask;
+  CpuFeatures::cross_compile_ |= mask;
 }
 
 
 PlatformFeatureScope::~PlatformFeatureScope() {
-  CpuFeatures::supported_ = old_supported_;
-  CpuFeatures::found_by_runtime_probing_only_ =
-      old_found_by_runtime_probing_only_;
+  CpuFeatures::cross_compile_ = old_cross_compile_;
 }