Get rid of ZoneScope completely.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 564fd7b64638694ba978725aa5776995a678f61a..476e405249974bc23cd73fdf83b98af439b51a4b 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -1738,7 +1738,6 @@ Isolate::Isolate()
       descriptor_lookup_cache_(NULL),
       handle_scope_implementer_(NULL),
       unicode_cache_(NULL),
-      runtime_zone_(this),
       in_use_list_(0),
       free_list_(0),
       preallocated_storage_preallocated_(false),
@@ -1935,9 +1934,6 @@ void Isolate::SetIsolateThreadLocals(Isolate* isolate,
 Isolate::~Isolate() {
   TRACE_ISOLATE(destructor);
 
-  // Has to be called while counters_ are still alive.
-  runtime_zone_.DeleteKeptSegment();
-
   delete[] assembler_spare_buffer_;
   assembler_spare_buffer_ = NULL;
 
@@ -2114,7 +2110,7 @@ bool Isolate::Init(Deserializer* des) {
   global_handles_ = new GlobalHandles(this);
   bootstrapper_ = new Bootstrapper(this);
   handle_scope_implementer_ = new HandleScopeImplementer(this);
-  stub_cache_ = new StubCache(this, runtime_zone());
+  stub_cache_ = new StubCache(this);
   regexp_stack_ = new RegExpStack();
   regexp_stack_->isolate_ = this;
   date_cache_ = new DateCache();