use a hash table for the function cache as blink is leaking functiontemplates

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 87cd0d4a0cca13da51dd2134e55dd7b1fd9b81b7..c5d59e66b67467d2cbe43969c7d4168b506a19b1 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -2117,7 +2117,9 @@ bool Genesis::InstallNatives() {
 
   InstallNativeFunctions();
 
-  native_context()->set_function_cache(heap()->empty_fixed_array());
+  auto function_cache =
+      ObjectHashTable::New(isolate(), ApiNatives::kInitialFunctionCacheSize);
+  native_context()->set_function_cache(*function_cache);
 
   // Store the map for the string prototype after the natives has been compiled
   // and the String function has been set up.