[strong] Introduce --use-strong flag

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index e8bb005dc8b8f46ae88b0b68dc75e3b5ef773e2f..7e85e59bdb169ea56e6fc862d7d21d01cd2defbe 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -15292,8 +15292,8 @@ Handle<Object> CompilationCacheTable::Lookup(Handle<String> src,
                                              Handle<Context> context) {
   Isolate* isolate = GetIsolate();
   Handle<SharedFunctionInfo> shared(context->closure()->shared());
-  StringSharedKey key(src, shared, FLAG_use_strict ? STRICT : SLOPPY,
-                      RelocInfo::kNoPosition);
+  LanguageMode mode = construct_language_mode(FLAG_use_strict, FLAG_use_strong);
+  StringSharedKey key(src, shared, mode, RelocInfo::kNoPosition);
   int entry = FindEntry(&key);
   if (entry == kNotFound) return isolate->factory()->undefined_value();
   int index = EntryToIndex(entry);
@@ -15333,8 +15333,8 @@ Handle<CompilationCacheTable> CompilationCacheTable::Put(
     Handle<Context> context, Handle<Object> value) {
   Isolate* isolate = cache->GetIsolate();
   Handle<SharedFunctionInfo> shared(context->closure()->shared());
-  StringSharedKey key(src, shared, FLAG_use_strict ? STRICT : SLOPPY,
-                      RelocInfo::kNoPosition);
+  LanguageMode mode = construct_language_mode(FLAG_use_strict, FLAG_use_strong);
+  StringSharedKey key(src, shared, mode, RelocInfo::kNoPosition);
   {
     Handle<Object> k = key.AsHandle(isolate);
     DisallowHeapAllocation no_allocation_scope;