dartjs: Remove unused isFromMainOutputUnit.

pkg/compiler/lib/src/deferred_load.dart

Index: pkg/compiler/lib/src/deferred_load.dart
diff --git a/pkg/compiler/lib/src/deferred_load.dart b/pkg/compiler/lib/src/deferred_load.dart
index 2cd08666d72248d7548290bca9c27f852bba9bca..5a02f036f51e3709186bcee8cca970077649de1f 100644
--- a/pkg/compiler/lib/src/deferred_load.dart
+++ b/pkg/compiler/lib/src/deferred_load.dart
@@ -213,10 +213,6 @@ class DeferredLoadTask extends CompilerTask {
     return outputUnitTo.imports.containsAll(outputUnitFrom.imports);
   }
 
-  bool isFromMainOutputUnit(Element element) {
-    return outputUnitForElement(element) == mainOutputUnit;
-  }
-
   void registerConstantDeferredUse(DeferredConstantValue constant,
                                    PrefixElement prefix) {
     OutputUnit outputUnit = new OutputUnit();