Split backend implementation of EnqueuerListener

pkg/compiler/lib/src/ssa/builder_kernel.dart

Index: pkg/compiler/lib/src/ssa/builder_kernel.dart
diff --git a/pkg/compiler/lib/src/ssa/builder_kernel.dart b/pkg/compiler/lib/src/ssa/builder_kernel.dart
index 226073f116a282e5d9536a6cf3566f81c986c043..179891c5c3d6e83fcfd09932a64f5f8e3bd0c577 100644
--- a/pkg/compiler/lib/src/ssa/builder_kernel.dart
+++ b/pkg/compiler/lib/src/ssa/builder_kernel.dart
@@ -2194,7 +2194,7 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
       return;
     }
 
-    if (!backend.hasIsolateSupport) {
+    if (!backend.backendUsage.isIsolateInUse) {
       // If the isolate library is not used, we just generate code
       // to fetch the static state.
       String name = backend.namer.staticStateHolder;
@@ -2223,7 +2223,7 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
 
     List<HInstruction> inputs = _visitPositionalArguments(invocation.arguments);
 
-    if (!backend.hasIsolateSupport) {
+    if (!backend.backendUsage.isIsolateInUse) {
       // If the isolate library is not used, we ignore the isolate argument and
       // just invoke the closure.
       push(new HInvokeClosure(new Selector.callClosure(0),
@@ -2691,7 +2691,7 @@ class KernelSsaBuilder extends ir.Visitor with GraphBuilder {
     ir.Class cls = _containingClass(invocation).superclass;
     assert(cls != null);
     ir.Procedure noSuchMethod = _findNoSuchMethodInClass(cls);
-    if (backend.hasInvokeOnSupport &&
+    if (backend.backendUsage.isInvokeOnUsed &&
         _containingClass(noSuchMethod) != astAdapter.objectClass) {
       // Register the call as dynamic if [noSuchMethod] on the super
       // class is _not_ the default implementation from [Object] (it might be