Reapply "This change makes it easier to put type parameters on JavaScript Arrays."

sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index 31b382dea9fb5b319cbad6d6141fb4b6e744418e..02e78b7fce8abee9707e54097758e1a4a53054b1 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -195,6 +195,7 @@ class JavaScriptBackend extends Backend {
   ClassElement jsExtendableArrayClass;
 
   Element jsIndexableLength;
+  Element jsArrayTypedConstructor;
   Element jsArrayRemoveLast;
   Element jsArrayAdd;
   Element jsStringSplit;
@@ -616,6 +617,7 @@ class JavaScriptBackend extends Backend {
     }
 
     jsArrayClass.ensureResolved(compiler);
+    jsArrayTypedConstructor = compiler.lookupElementIn(jsArrayClass, 'typed');
     jsArrayRemoveLast = compiler.lookupElementIn(jsArrayClass, 'removeLast');
     jsArrayAdd = compiler.lookupElementIn(jsArrayClass, 'add');