Split backend implementation of EnqueuerListener

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 b99358bd026a5f8f857dc2db517cb1377bf1f123..7cabd5b4e74d0814d8d9fb9a68fd758d3898cd87 100644
--- a/pkg/compiler/lib/src/js_backend/backend_usage.dart
+++ b/pkg/compiler/lib/src/js_backend/backend_usage.dart
@@ -20,6 +20,21 @@ abstract class BackendUsage {
   bool get needToInitializeDispatchProperty;
   bool usedByBackend(Element element);
   Iterable<Element> get globalDependencies;
+
+  /// True if a core-library function requires the preamble file to function.
+  bool get requiresPreamble;
+
+  /// `true` if access to [BackendHelpers.invokeOnMethod] is supported.
+  bool get hasInvokeOnSupport;

[Siggi Cherem (dart-lang), 2017/02/17 23:05:08]

Let's rename a lot of these properties.

Reading the changes throughout the CL I felt that it was really odd to ask a
`backendUsage` about whether or not something is supported :).  Then I realized
that this is not about something being supported (all of these features are
always supported) but about whether some features are used and therefore we must
reason about them elsewhere.

Here is a proposal for new names:
- hasInvokeOnSupport => isInvokeOnUsed
- hasRuntimeTypeSupport => isRuntimeTypeUsed
- hasIsolateSupport => isIsolateInUse
- hasFunctionApplySupport => isFunctionApplyUsed

I'm OK doing this as a follow up change if you prefer.

[Johnni Winther, 2017/02/20 11:37:42]

Done.

+
+  /// `true` of `Object.runtimeType` is supported.
+  bool get hasRuntimeTypeSupport;
+
+  /// `true` of use of the `dart:isolate` library is supported.
+  bool get hasIsolateSupport;
+
+  /// `true` of `Function.apply` is supported.
+  bool get hasFunctionApplySupport;
 }
 
 abstract class BackendUsageBuilder {
@@ -35,6 +50,14 @@ abstract class BackendUsageBuilder {
       {bool isGlobal: false});
   WorldImpact createImpactFor(BackendImpact impact);
   void registerUsedMember(MemberElement member);
+
+  bool hasRuntimeTypeSupport;
+
+  /// `true` of use of the `dart:isolate` library is supported.
+  bool hasIsolateSupport;
+
+  /// `true` of `Function.apply` is supported.
+  bool hasFunctionApplySupport;
 }
 
 class BackendUsageImpl implements BackendUsage, BackendUsageBuilder {
@@ -50,6 +73,21 @@ class BackendUsageImpl implements BackendUsage, BackendUsageBuilder {
   bool _needToInitializeIsolateAffinityTag = false;
   bool _needToInitializeDispatchProperty = false;
 
+  /// True if a core-library function requires the preamble file to function.
+  bool requiresPreamble = false;
+
+  /// `true` if access to [BackendHelpers.invokeOnMethod] is supported.
+  bool hasInvokeOnSupport = false;
+
+  /// `true` of `Object.runtimeType` is supported.
+  bool hasRuntimeTypeSupport = false;
+
+  /// `true` of use of the `dart:isolate` library is supported.
+  bool hasIsolateSupport = false;
+
+  /// `true` of `Function.apply` is supported.
+  bool hasFunctionApplySupport = false;
+
   BackendUsageImpl(this._commonElements, this._helpers, this._resolution);
 
   bool get needToInitializeIsolateAffinityTag =>
@@ -196,6 +234,12 @@ class BackendUsageImpl implements BackendUsage, BackendUsageBuilder {
   void registerUsedMember(MemberElement member) {
     if (member == _helpers.getIsolateAffinityTagMarker) {
       _needToInitializeIsolateAffinityTag = true;
+    } else if (member == _helpers.requiresPreambleMarker) {
+      requiresPreamble = true;
+    } else if (member == _helpers.invokeOnMethod) {
+      hasInvokeOnSupport = true;
+    } else if (_commonElements.isFunctionApplyMethod(member)) {
+      hasFunctionApplySupport = true;
     }
   }