Small cleanups in the Kernel FlowGraphBuilder

runtime/vm/kernel_to_il.h

Index: runtime/vm/kernel_to_il.h
diff --git a/runtime/vm/kernel_to_il.h b/runtime/vm/kernel_to_il.h
index b3cc17473a94948c57ac99d0eb0d367bb83e451d..ec5bfd494c06b63eb02c5b143fefadf8f5ba75ad 100644
--- a/runtime/vm/kernel_to_il.h
+++ b/runtime/vm/kernel_to_il.h
@@ -188,12 +188,12 @@ class ActiveFunctionScope {
 
 class TranslationHelper {
  public:
-  TranslationHelper(dart::Thread* thread, dart::Zone* zone, Isolate* isolate)
+  explicit TranslationHelper(dart::Thread* thread)
       : thread_(thread),
-        zone_(zone),
-        isolate_(isolate),
-        allocation_space_(thread_->IsMutatorThread() ? Heap::kNew
-                                                     : Heap::kOld) {}
+        zone_(thread->zone()),
+        isolate_(thread->isolate()),
+        allocation_space_(thread->IsMutatorThread() ? Heap::kNew : Heap::kOld) {
+  }
   virtual ~TranslationHelper() {}
 
   Thread* thread() { return thread_; }
@@ -519,8 +519,8 @@ class ScopeBuilder : public RecursiveVisitor {
       : result_(NULL),
         parsed_function_(parsed_function),
         node_(node),
-        zone_(Thread::Current()->zone()),
-        translation_helper_(Thread::Current(), zone_, Isolate::Current()),
+        translation_helper_(Thread::Current()),
+        zone_(translation_helper_.zone()),
         type_translator_(&translation_helper_,
                          &active_class_,
                          /*finalize=*/true),
@@ -615,8 +615,8 @@ class ScopeBuilder : public RecursiveVisitor {
 
   ActiveClass active_class_;
 
-  Zone* zone_;
   TranslationHelper translation_helper_;
+  Zone* zone_;
   DartTypeTranslator type_translator_;
 
   FunctionNode* current_function_node_;
@@ -628,7 +628,7 @@ class ScopeBuilder : public RecursiveVisitor {
 };
 
 
-class FlowGraphBuilder : public TreeVisitor {
+class FlowGraphBuilder : public ExpressionVisitor, public StatementVisitor {
  public:
   FlowGraphBuilder(TreeNode* node,
                    ParsedFunction* parsed_function,
@@ -640,7 +640,8 @@ class FlowGraphBuilder : public TreeVisitor {
 
   FlowGraph* BuildGraph();
 
-  virtual void VisitDefaultTreeNode(TreeNode* node) { UNREACHABLE(); }
+  virtual void VisitDefaultExpression(Expression* node) { UNREACHABLE(); }
+  virtual void VisitDefaultStatement(Statement* node) { UNREACHABLE(); }
 
   virtual void VisitInvalidExpression(InvalidExpression* node);
   virtual void VisitNullLiteral(NullLiteral* node);
@@ -676,7 +677,6 @@ class FlowGraphBuilder : public TreeVisitor {
   virtual void VisitLet(Let* node);
   virtual void VisitThrow(Throw* node);
   virtual void VisitRethrow(Rethrow* node);
-  virtual void VisitBlockExpression(BlockExpression* node);
 
   virtual void VisitInvalidStatement(InvalidStatement* node);
   virtual void VisitEmptyStatement(EmptyStatement* node);
@@ -854,8 +854,8 @@ class FlowGraphBuilder : public TreeVisitor {
 
   void InlineBailout(const char* reason);
 
-  Zone* zone_;
   TranslationHelper translation_helper_;
+  Zone* zone_;
 
   // The node we are currently compiling (e.g. FunctionNode, Constructor,
   // Field)