Overhaul tree IR visitor and rename IR classes.

pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart

Index: pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
diff --git a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
index ad6a31e246209b973ab3d61c587ad5af438642b6..d4e93781ddcbbba84a708e062fc45f0520a91837 100644
--- a/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
+++ b/pkg/compiler/lib/src/tree_ir/tree_ir_tracer.dart
@@ -58,17 +58,8 @@ class BlockCollector extends StatementVisitor {
     blocks.add(block);
   }
 
-  void collect(ExecutableDefinition node) {
-    if (node.body != null) {
-      if (node is ConstructorDefinition) {
-        for (Initializer initializer in node.initializers) {
-          if (initializer is FieldInitializer) {
-            visitStatement(initializer.body);
-          }
-        }
-      }
-      visitStatement(node.body);
-    }
+  void collect(RootNode node) {
+    node.forEachBody(visitStatement);
   }
 
   visitLabeledStatement(LabeledStatement node) {
@@ -183,7 +174,7 @@ class BlockCollector extends StatementVisitor {
 
 }
 
-class TreeTracer extends TracerUtil with StatementVisitor, PassMixin {
+class TreeTracer extends TracerUtil with StatementVisitor {
   // TODO(asgerf): Fix visitors so we don't have to use PassMixin here.

[Kevin Millikin (Google), 2015/04/08 15:10:16]

I think you can remove this TODO.

[asgerf, 2015/04/09 09:58:23]

Done.

   String get passName => null;
 
@@ -195,18 +186,16 @@ class TreeTracer extends TracerUtil with StatementVisitor, PassMixin {
   BlockCollector collector;
   int statementCounter;
 
-  void traceGraph(String name, ExecutableDefinition node) {
-    if (node is FunctionDefinition && node.isAbstract) return;
-    if (node is FieldDefinition && node.body == null) return;
+  void traceGraph(String name, RootNode node) {
+    if (node.isEmpty) return;
     tag("cfg", () {
       printProperty("name", name);
-      rewrite(node);
+      printRootNode(node);
       collector.blocks.forEach(printBlock);
     });
   }
 
-  @override
-  void rewriteExecutableDefinition(ExecutableDefinition node) {
+  void printRootNode(RootNode node) {
     collector = new BlockCollector();
     names = new Names();
     statementCounter = 0;