Incremental compilation of constants.

dart/pkg/dart2js_incremental/lib/library_updater.dart

Index: dart/pkg/dart2js_incremental/lib/library_updater.dart
diff --git a/dart/pkg/dart2js_incremental/lib/library_updater.dart b/dart/pkg/dart2js_incremental/lib/library_updater.dart
index 345d190cbc51dab315889de75bd3bbabd2023116..382ec1b9207c5c2a7826093fa6ad718a823cbe67 100644
--- a/dart/pkg/dart2js_incremental/lib/library_updater.dart
+++ b/dart/pkg/dart2js_incremental/lib/library_updater.dart
@@ -75,6 +75,9 @@ import 'package:compiler/src/elements/modelx.dart' show
 import 'package:compiler/src/universe/universe.dart' show
     Selector;
 
+import 'package:compiler/src/constants/values.dart' show
+    ConstantValue;
+
 import 'diff.dart' show
     Difference,
     computeDifference;
@@ -129,6 +132,10 @@ class LibraryUpdater extends JsFeatures {
 
   final Set<ClassElementX> _directlyInstantiatedClasses;
 
+  final Set<ConstantValue> _compiledConstants;
+
+  bool _hasComputedNeeds = false;
+
   LibraryUpdater(
       Compiler compiler,
       this.inputProvider,
@@ -138,7 +145,9 @@ class LibraryUpdater extends JsFeatures {
       : this.compiler = compiler,
         _emittedClasses = new Set.from(compiler.backend.emitter.neededClasses),
         _directlyInstantiatedClasses = new Set.from(
-            compiler.codegenWorld.directlyInstantiatedClasses);
+            compiler.codegenWorld.directlyInstantiatedClasses),
+        _compiledConstants = new Set<ConstantValue>.identity()..addAll(
+            compiler.backend.constants.compiledConstants);
 
   /// When [true], updates must be applied (using [applyUpdates]) before the
   /// [compiler]'s state correctly reflects the updated program.
@@ -602,7 +611,7 @@ class LibraryUpdater extends JsFeatures {
     if (!newClasses.isEmpty) {
       // Ask the emitter to compute "needs" (only) if new classes were
       // instantiated.
-      emitter.computeNeeds();
+      _ensureNeedsComputed();
       newClasses = new Set.from(emitter.neededClasses);
       newClasses.removeAll(_emittedClasses);
     } else {
@@ -661,6 +670,25 @@ class LibraryUpdater extends JsFeatures {
       }
     }
 
+    Set<ConstantValue> newConstants = new Set<ConstantValue>.identity()..addAll(
+        compiler.backend.constants.compiledConstants);
+    newConstants.removeAll(_compiledConstants);
+
+    if (!newConstants.isEmpty) {
+      _ensureNeedsComputed();
+      List<ConstantValue> constants =
+          emitter.outputConstantLists[compiler.deferredLoadTask.mainOutputUnit];
+      if (constants != null) {
+        for (ConstantValue constant in constants) {
+          if (newConstants.contains(constant)) {
+            jsAst.Statement constantInitializer = emitter.oldEmitter
+                .buildConstantInitializer(constant).toStatement();
+            updates.add(constantInitializer);
+          }
+        }
+      }
+    }
+
     updates.add(js.statement(r'''
 if (self.$dart_unsafe_eval.pendingStubs) {
   self.$dart_unsafe_eval.pendingStubs.map(function(e) { return e(); });
@@ -764,6 +792,12 @@ if (self.$dart_unsafe_eval.pendingStubs) {
   List<String> computeFields(ClassElement cls) {
     return new EmitterHelper(compiler).computeFields(cls);
   }
+
+  void _ensureNeedsComputed() {
+    if (_hasComputedNeeds) return;
+    emitter.computeNeeds();
+    _hasComputedNeeds = true;
+  }
 }
 
 /// Represents an update (aka patch) of [before] to [after]. We use the word