Introduce subclass wrappers for STL containers that make them a lot easier

src/compiler/structured-machine-assembler.h

Index: src/compiler/structured-machine-assembler.h
diff --git a/src/compiler/structured-machine-assembler.h b/src/compiler/structured-machine-assembler.h
index a6cb8ca88b1896dca8b683f63eb4e616f142c18c..6bac9cd31c984ca0a0d2bf41109ffa4fec31de09 100644
--- a/src/compiler/structured-machine-assembler.h
+++ b/src/compiler/structured-machine-assembler.h
@@ -101,8 +101,7 @@ class StructuredMachineAssembler
  private:
   bool ScheduleValid() { return schedule_ != NULL; }
 
-  typedef std::vector<Environment*, zone_allocator<Environment*> >
-      EnvironmentVector;
+  typedef ZoneVector<Environment*> EnvironmentVector;
 
   NodeVector* CurrentVars() { return &current_environment_->variables_; }
   Node*& VariableAt(Environment* environment, int offset);
@@ -124,9 +123,6 @@ class StructuredMachineAssembler
   void MergeBackEdgesToLoopHeader(Environment* header,
                                   EnvironmentVector* environments);
 
-  typedef std::vector<MachineType, zone_allocator<MachineType> >
-      RepresentationVector;
-
   Schedule* schedule_;
   MachineOperatorBuilder machine_;
   CommonOperatorBuilder common_;
@@ -214,12 +210,10 @@ class StructuredMachineAssembler::IfBuilder {
     int pending_else_size_;
   };
 
-  typedef std::vector<ExpressionState, zone_allocator<ExpressionState> >
-      ExpressionStates;
-  typedef std::vector<UnresolvedBranch*, zone_allocator<UnresolvedBranch*> >
-      PendingMergeStack;
+  typedef ZoneVector<ExpressionState> ExpressionStates;
+  typedef ZoneVector<UnresolvedBranch*> PendingMergeStack;
   struct IfClause;
-  typedef std::vector<IfClause*, zone_allocator<IfClause*> > IfClauses;
+  typedef ZoneVector<IfClause*> IfClauses;
 
   struct PendingMergeStackRange {
     PendingMergeStack* merge_stack_;