dart2js cps: Refactor tracking of side effects.

pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart

Index: pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart
diff --git a/pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart b/pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart
index 6f733e31f02e5df72ad70f907d39342804537361..e03f9cad33bc96a02b3daaa241c94945cdb25fd9 100644
--- a/pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart
+++ b/pkg/compiler/lib/src/cps_ir/eagerly_load_statics.dart
@@ -7,6 +7,7 @@ library dart2js.cps_ir.eagerly_load_statics;
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart' show Pass;
 import '../elements/elements.dart';
+import 'cps_fragment.dart';
 
 /// Replaces [GetLazyStatic] with [GetStatic] when the static field is known
 /// to have been initialized.
@@ -30,6 +31,12 @@ class EagerlyLoadStatics extends TrampolineRecursiveVisitor implements Pass {
     visit(node.body);
   }
 
+  Expression traverseLetPrim(LetPrim node) {
+    Expression next = node.body;
+    visit(node.primitive);
+    return next;
+  }
+
   Expression traverseLetCont(LetCont node) {
     for (Continuation cont in node.continuations) {
       initializersAt[cont] = cloneFieldMap(initializerFor);
@@ -51,10 +58,13 @@ class EagerlyLoadStatics extends TrampolineRecursiveVisitor implements Pass {
 
   void visitGetLazyStatic(GetLazyStatic node) {
     Primitive initializer = initializerFor[node.element];
-    if (initializer != null) {
-      GetStatic newNode = new GetStatic.witnessed(node.element, initializer,
-          node.sourceInformation);
-      newNode.type = node.type;
+    if (initializer is GetLazyStatic && initializer.isFinal) {
+      // No reason to create a GetStatic when the field is final.
+      node.replaceWithFragment(new CpsFragment(), initializer);
+    } else if (initializer != null) {
+      GetStatic newNode = new GetStatic.witnessed(node.element,
+          initializer, sourceInformation: node.sourceInformation)
+          ..type = node.type;
       node.replaceWith(newNode);
     } else {
       initializerFor[node.element] = node;