One Zone per CompilationInfo.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 5ca2b87f0e011a6a76afc281979291f18d96d9df..8717c990ba4d9c3df354d9c896201c19db5fcf55 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -850,7 +850,7 @@ class Isolate {
     ASSERT(handle_scope_implementer_);
     return handle_scope_implementer_;
   }
-  Zone* zone() { return &zone_; }
+  Zone* runtime_zone() { return &runtime_zone_; }
 
   UnicodeCache* unicode_cache() {
     return unicode_cache_;
@@ -1196,7 +1196,7 @@ class Isolate {
   v8::ImplementationUtilities::HandleScopeData handle_scope_data_;
   HandleScopeImplementer* handle_scope_implementer_;
   UnicodeCache* unicode_cache_;
-  Zone zone_;
+  Zone runtime_zone_;
   PreallocatedStorage in_use_list_;
   PreallocatedStorage free_list_;
   bool preallocated_storage_preallocated_;