Thread/Isolate refactoring: new(Isolate) -> new(Zone)

runtime/vm/flow_graph_builder.h

Index: runtime/vm/flow_graph_builder.h
===================================================================
--- runtime/vm/flow_graph_builder.h	(revision 44266)
+++ runtime/vm/flow_graph_builder.h	(working copy)
@@ -131,6 +131,7 @@
                           intptr_t try_index);
 
   Isolate* isolate() const { return caller_graph_->isolate(); }
+  Zone* zone() const { return caller_graph_->zone(); }
 
   FlowGraph* caller_graph_;
   Definition* call_;
@@ -230,6 +231,7 @@
   static uword FindDoubleConstant(double value);
 
   Isolate* isolate() const { return parsed_function().isolate(); }
+  Zone* zone() const { return parsed_function().zone(); }
 
  private:
   friend class NestedStatement;  // Explicit access to nesting_stack_.
@@ -480,6 +482,7 @@
                       JoinEntryInstr* target);
 
   Isolate* isolate() const { return owner()->isolate(); }
+  Zone* zone() const { return owner()->zone(); }
 
  private:
   friend class TempLocalScope;  // For ReturnDefinition.