Compute frontend/backend specific constants.

sdk/lib/_internal/compiler/implementation/deferred_load.dart

Index: sdk/lib/_internal/compiler/implementation/deferred_load.dart
diff --git a/sdk/lib/_internal/compiler/implementation/deferred_load.dart b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
index 8585c4825134d354927f55558c5f9eff19717d6f..294fb34711d5617e3d287a62db580380720d297f 100644
--- a/sdk/lib/_internal/compiler/implementation/deferred_load.dart
+++ b/sdk/lib/_internal/compiler/implementation/deferred_load.dart
@@ -5,6 +5,7 @@
 library deferred_load;
 
 import 'dart2jslib.dart' show
+    Backend,
     Compiler,
     CompilerTask,
     Constant,
@@ -150,6 +151,8 @@ class DeferredLoadTask extends CompilerTask {
 
   DeferredLoadTask(Compiler compiler) : super(compiler);
 
+  Backend get backend => compiler.backend;
+
   /// Returns the [OutputUnit] where [element] belongs.
   OutputUnit outputUnitForElement(Element element) {
     if (!splitProgram) return mainOutputUnit;
@@ -292,7 +295,11 @@ class DeferredLoadTask extends CompilerTask {
       if (dependency.isStatement()) continue;
       elementDependencies.add(dependency);
     }
-    constantDependencies.addAll(elements.allConstants);
+    elements.forEachConstantNode((Node n, _) {
+      // Explicitly depend on the backend constants.
+      constantDependencies.add(
+          backend.constants.getConstantForNode(n, elements));
+    });
     elementDependencies.addAll(elements.otherDependencies);
   }
 
@@ -305,9 +312,10 @@ class DeferredLoadTask extends CompilerTask {
       Set<Constant> constants) {
     // TODO(sigurdm): How is metadata on a patch-class handled?
     for (MetadataAnnotation metadata in element.metadata) {
-      if (metadata.value != null) {
-        constants.add(metadata.value);
-        elements.add(metadata.value.computeType(compiler).element);
+      Constant constant = backend.constants.getConstantForMetadata(metadata);
+      if (constant != null) {
+        constants.add(constant);
+        elements.add(constant.computeType(compiler).element);
       }
     }
     if (element.isClass()) {
@@ -419,15 +427,19 @@ class DeferredLoadTask extends CompilerTask {
         // TODO(sigurdm): The metadata should go to the right output unit.
         // For now they all go to the main output unit.
         for (MetadataAnnotation metadata in library.metadata) {
-          if (metadata.value != null) {
-            _mapDependencies(metadata.value.computeType(compiler).element,
+          Constant constant =
+              backend.constants.getConstantForMetadata(metadata);
+          if (constant != null) {
+            _mapDependencies(constant.computeType(compiler).element,
                 _fakeMainImport);
           }
         }
         for (LibraryTag tag in library.tags) {
           for (MetadataAnnotation metadata in tag.metadata) {
-            if (metadata.value != null) {
-              _mapDependencies(metadata.value.computeType(compiler).element,
+            Constant constant =
+                backend.constants.getConstantForMetadata(metadata);
+            if (constant != null) {
+              _mapDependencies(constant.computeType(compiler).element,
                   _fakeMainImport);
             }
           }
@@ -596,8 +608,7 @@ class DeferredLoadTask extends CompilerTask {
         for (MetadataAnnotation metadata in metadatas) {
           metadata.ensureResolved(compiler);
           Element element = metadata.value.computeType(compiler).element;
-          if (metadata.value.computeType(compiler).element ==
-              deferredLibraryClass) {
+          if (element == deferredLibraryClass) {
             ConstructedConstant constant = metadata.value;
             StringConstant s = constant.fields[0];
             result = s.value.slowToString();
@@ -766,7 +777,7 @@ class DeferredLoadTask extends CompilerTask {
         }
       });
     }
-    if (splitProgram && compiler.backend is DartBackend) {
+    if (splitProgram && backend is DartBackend) {
       // TODO(sigurdm): Implement deferred loading for dart2dart.
       splitProgram = false;
       compiler.reportInfo(