Replaced different means of zone pooling/reusing by one zone segment pool

src/isolate.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_ISOLATE_H_
 #define V8_ISOLATE_H_
 
 #include <memory>
 #include <queue>
 
@@ skipping 875 matching lines @@
   DescriptorLookupCache* descriptor_lookup_cache() {
     return descriptor_lookup_cache_;
   }
 
   HandleScopeData* handle_scope_data() { return &handle_scope_data_; }
 
   HandleScopeImplementer* handle_scope_implementer() {
     DCHECK(handle_scope_implementer_);
     return handle_scope_implementer_;
   }
-  Zone* runtime_zone() { return runtime_zone_; }
 
   UnicodeCache* unicode_cache() {
     return unicode_cache_;
   }
 
   InnerPointerToCodeCache* inner_pointer_to_code_cache() {
     return inner_pointer_to_code_cache_;
   }
 
   GlobalHandles* global_handles() { return global_handles_; }
@@ skipping 420 matching lines @@
   bool capture_stack_trace_for_uncaught_exceptions_;
   int stack_trace_for_uncaught_exceptions_frame_limit_;
   StackTrace::StackTraceOptions stack_trace_for_uncaught_exceptions_options_;
   KeyedLookupCache* keyed_lookup_cache_;
   ContextSlotCache* context_slot_cache_;
   DescriptorLookupCache* descriptor_lookup_cache_;
   HandleScopeData handle_scope_data_;
   HandleScopeImplementer* handle_scope_implementer_;
   UnicodeCache* unicode_cache_;
   AccountingAllocator* allocator_;
-  Zone* runtime_zone_;
   InnerPointerToCodeCache* inner_pointer_to_code_cache_;
   GlobalHandles* global_handles_;
   EternalHandles* eternal_handles_;
   ThreadManager* thread_manager_;
   RuntimeState runtime_state_;
   Builtins builtins_;
   bool has_installed_extensions_;
   unibrow::Mapping<unibrow::Ecma262UnCanonicalize> jsregexp_uncanonicalize_;
   unibrow::Mapping<unibrow::CanonicalizationRange> jsregexp_canonrange_;
   unibrow::Mapping<unibrow::Ecma262Canonicalize>
@@ skipping 338 matching lines @@
 
   EmbeddedVector<char, 128> filename_;
   FILE* file_;
   int scope_depth_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_ISOLATE_H_