Change the type inference for fields in dart2js

lib/compiler/implementation/ssa/codegen.dart

Index: lib/compiler/implementation/ssa/codegen.dart
diff --git a/lib/compiler/implementation/ssa/codegen.dart b/lib/compiler/implementation/ssa/codegen.dart
index 087d657c4b2aaf64440db5358589fa36574014c3..38681f914948b5fe7da8b54006f8b205f5d224df 100644
--- a/lib/compiler/implementation/ssa/codegen.dart
+++ b/lib/compiler/implementation/ssa/codegen.dart
@@ -1634,33 +1634,13 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
   }
 
   visitFieldSet(HFieldSet node) {
-    if (work.element.isGenerativeConstructorBody() &&
-        node.element.isMember() &&
-        node.value.hasGuaranteedType() &&
-        node.block.dominates(currentGraph.exit)) {
-      backend.updateFieldConstructorSetters(node.element,
-                                            node.value.guaranteedType);
-    }
     String name = backend.namer.getName(node.element);
     DartType type = types[node.receiver].computeType(compiler);
     if (type != null) {
       if (!work.element.isGenerativeConstructorBody()) {
         world.registerFieldSetter(
             node.element.name, node.element.getLibrary(), type);
-      }
-      // Determine the types seen so far for the field. If only number
-      // types have been seen and the value of the field set is a
-      // simple number computation only depending on that field, we
-      // can safely keep the number type for the field.
-      HType fieldSettersType = backend.fieldSettersTypeSoFar(node.element);
-      HType initializersType =
-          backend.typeFromInitializersSoFar(node.element);
-      HType fieldType = fieldSettersType.union(initializersType);
-      if (HType.NUMBER.union(fieldType) == HType.NUMBER &&
-          isSimpleFieldNumberComputation(node.value, node)) {
-        backend.updateFieldSetters(node.element, HType.NUMBER);
-      } else {
-        backend.updateFieldSetters(node.element, types[node.value]);
+        backend.registerFieldSetter(node, types);
       }
     }
     use(node.receiver);
@@ -1699,14 +1679,6 @@ class SsaCodeGenerator implements HVisitor, HBlockInformationVisitor {
   }
 
   visitForeignNew(HForeignNew node) {
-    int j = 0;
-    node.element.forEachInstanceField(
-      includeBackendMembers: true,
-      includeSuperMembers: true,
-      f: (ClassElement enclosingClass, Element member) {
-        backend.updateFieldInitializers(member, types[node.inputs[j]]);
-        j++;
-      });
     String jsClassReference = backend.namer.isolateAccess(node.element);
     List<HInstruction> inputs = node.inputs;
     // We can't use 'visitArguments', since our arguments start at input[0].