Merge CommonElements and BackendHelpers!

pkg/compiler/lib/src/js_backend/backend_usage.dart

Index: pkg/compiler/lib/src/js_backend/backend_usage.dart
diff --git a/pkg/compiler/lib/src/js_backend/backend_usage.dart b/pkg/compiler/lib/src/js_backend/backend_usage.dart
index 869833e43e4f3eea378c9840ba8ff1e6f34d853e..0f1a3f3a51b92e8d5094a381a6ef8e3750b4715d 100644
--- a/pkg/compiler/lib/src/js_backend/backend_usage.dart
+++ b/pkg/compiler/lib/src/js_backend/backend_usage.dart
@@ -8,7 +8,6 @@ import '../elements/elements.dart' show Element;
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../util/util.dart' show Setlet;
-import 'backend_helpers.dart';
 import 'backend_impact.dart';
 
 abstract class BackendUsage {
@@ -29,7 +28,7 @@ abstract class BackendUsage {
   /// `true` if a core-library function requires the preamble file to function.
   bool get requiresPreamble;
 
-  /// `true` if [BackendHelpers.invokeOnMethod] is used.
+  /// `true` if [CommonElements.invokeOnMethod] is used.
   bool get isInvokeOnUsed;
 
   /// `true` of `Object.runtimeType` is used.
@@ -88,7 +87,6 @@ abstract class BackendUsageBuilder {
 
 class BackendUsageBuilderImpl implements BackendUsageBuilder {
   final CommonElements _commonElements;
-  final BackendHelpers _helpers;
   // TODO(johnniwinther): Remove the need for these.
   Setlet<FunctionEntity> _globalFunctionDependencies;
   Setlet<ClassEntity> _globalClassDependencies;
@@ -105,7 +103,7 @@ class BackendUsageBuilderImpl implements BackendUsageBuilder {
   /// `true` if a core-library function requires the preamble file to function.
   bool requiresPreamble = false;
 
-  /// `true` if [BackendHelpers.invokeOnMethod] is used.
+  /// `true` if [CommonElements.invokeOnMethod] is used.
   bool isInvokeOnUsed = false;
 
   /// `true` of `Object.runtimeType` is used.
@@ -120,7 +118,7 @@ class BackendUsageBuilderImpl implements BackendUsageBuilder {
   /// `true` if `noSuchMethod` is used.
   bool isNoSuchMethodUsed = false;
 
-  BackendUsageBuilderImpl(this._commonElements, this._helpers);
+  BackendUsageBuilderImpl(this._commonElements);
 
   @override
   void registerBackendFunctionUse(FunctionEntity element) {
@@ -147,9 +145,9 @@ class BackendUsageBuilderImpl implements BackendUsageBuilder {
           (element.library.isPlatformLibrary &&
               element.sourcePosition.uri.path
                   .contains('_internal/js_runtime/lib/')) ||
-          element.library == _helpers.jsHelperLibrary ||
-          element.library == _helpers.interceptorsLibrary ||
-          element.library == _helpers.isolateHelperLibrary) {
+          element.library == _commonElements.jsHelperLibrary ||
+          element.library == _commonElements.interceptorsLibrary ||
+          element.library == _commonElements.isolateHelperLibrary) {
         // TODO(johnniwinther): We should be more precise about these.
         return true;
       } else {
@@ -162,25 +160,25 @@ class BackendUsageBuilderImpl implements BackendUsageBuilder {
 
   bool _isValidEntity(Entity element) {
     if (element is ConstructorEntity &&
-        (element == _helpers.streamIteratorConstructor ||
+        (element == _commonElements.streamIteratorConstructor ||
             _commonElements.isSymbolConstructor(element) ||
-            _helpers.isSymbolValidatedConstructor(element) ||
-            element == _helpers.syncCompleterConstructor)) {
+            _commonElements.isSymbolValidatedConstructor(element) ||
+            element == _commonElements.syncCompleterConstructor)) {
       // TODO(johnniwinther): These are valid but we could be more precise.
       return true;
     } else if (element == _commonElements.symbolClass ||
-        element == _helpers.objectNoSuchMethod) {
+        element == _commonElements.objectNoSuchMethod) {
       // TODO(johnniwinther): These are valid but we could be more precise.
       return true;
     } else if (element == _commonElements.listClass ||
-        element == _helpers.mapLiteralClass ||
+        element == _commonElements.mapLiteralClass ||
         element == _commonElements.functionClass ||
         element == _commonElements.stringClass) {
       // TODO(johnniwinther): Avoid these.
       return true;
-    } else if (element == _helpers.genericNoSuchMethod ||
-        element == _helpers.unresolvedConstructorError ||
-        element == _helpers.malformedTypeError) {
+    } else if (element == _commonElements.genericNoSuchMethod ||
+        element == _commonElements.unresolvedConstructorError ||
+        element == _commonElements.malformedTypeError) {
       return true;
     }
     return false;
@@ -235,11 +233,11 @@ class BackendUsageBuilderImpl implements BackendUsageBuilder {
   }
 
   void registerUsedMember(MemberEntity member) {
-    if (member == _helpers.getIsolateAffinityTagMarker) {
+    if (member == _commonElements.getIsolateAffinityTagMarker) {
       _needToInitializeIsolateAffinityTag = true;
-    } else if (member == _helpers.requiresPreambleMarker) {
+    } else if (member == _commonElements.requiresPreambleMarker) {
       requiresPreamble = true;
-    } else if (member == _helpers.invokeOnMethod) {
+    } else if (member == _commonElements.invokeOnMethod) {
       isInvokeOnUsed = true;
     } else if (_commonElements.isFunctionApplyMethod(member)) {
       isFunctionApplyUsed = true;
@@ -296,7 +294,7 @@ class BackendUsageImpl implements BackendUsage {
   /// `true` if a core-library function requires the preamble file to function.
   final bool requiresPreamble;
 
-  /// `true` if [BackendHelpers.invokeOnMethod] is used.
+  /// `true` if [CommonElements.invokeOnMethod] is used.
   final bool isInvokeOnUsed;
 
   /// `true` of `Object.runtimeType` is used.