[dart2js] Use addUnused method for unused fields in proto shaker

The call to the new method has fewer arguments, which helps code size.

Change-Id: I50668e54bfba07ac34e8db99a748f7d83c6e5be4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/378382
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

pkg/compiler/lib/src/ir/protobuf_impacts.dart

@@ -112,6 +112,10 @@ class ProtobufImpactHandler implements ConditionalImpactHandler {
           _builderInfoAddMethod.getterType as ir.FunctionType,
           const <ir.DartType>[ir.NullType()]);
 
+  late final ir.Procedure? _builderInfoAddUnusedMethod = _elementMap
+      .env.libraryIndex
+      .tryGetProcedure(protobufLibraryUri, 'BuilderInfo', 'addUnused');
+
   static const String metadataFieldName = '_i';
 
   // All of those methods have the dart field name as second positional
@@ -142,25 +146,39 @@ class ProtobufImpactHandler implements ConditionalImpactHandler {
 
   ir.InstanceInvocation _buildProtobufMetadataPlaceholder(
       ir.InstanceInvocation node) {
-    return ir.InstanceInvocation(
-        ir.InstanceAccessKind.Instance,
-        _CloneVisitorLenientVariables().clone(node.receiver),
-        _builderInfoAddMethod.name,
-        ir.Arguments(
-          <ir.Expression>[
-            ir.IntLiteral(0), // tagNumber
-            ir.NullLiteral(), // name
-            ir.NullLiteral(), // fieldType
-            ir.NullLiteral(), // defaultOrMaker
-            ir.NullLiteral(), // subBuilder
-            ir.NullLiteral(), // valueOf
-            ir.NullLiteral(), // enumValues
-          ],
-          types: <ir.DartType>[const ir.NullType()],
-        ),
-        interfaceTarget: _builderInfoAddMethod,
-        functionType: _typeOfBuilderInfoAddOfNull)
-      ..fileOffset = node.fileOffset;
+    final addUnusedMethod = _builderInfoAddUnusedMethod;
+    if (addUnusedMethod == null) {
+      // Legacy version, call `add` method.
+      return ir.InstanceInvocation(
+          ir.InstanceAccessKind.Instance,
+          _CloneVisitorLenientVariables().clone(node.receiver),
+          _builderInfoAddMethod.name,
+          ir.Arguments(
+            <ir.Expression>[
+              ir.IntLiteral(0), // tagNumber
+              ir.NullLiteral(), // name
+              ir.NullLiteral(), // fieldType
+              ir.NullLiteral(), // defaultOrMaker
+              ir.NullLiteral(), // subBuilder
+              ir.NullLiteral(), // valueOf
+              ir.NullLiteral(), // enumValues
+            ],
+            types: <ir.DartType>[const ir.NullType()],
+          ),
+          interfaceTarget: _builderInfoAddMethod,
+          functionType: _typeOfBuilderInfoAddOfNull)
+        ..fileOffset = node.fileOffset;
+    } else {
+      // New version, call `addUnused` method.
+      return ir.InstanceInvocation(
+          ir.InstanceAccessKind.Instance,
+          _CloneVisitorLenientVariables().clone(node.receiver),
+          addUnusedMethod.name,
+          ir.Arguments([]),
+          interfaceTarget: addUnusedMethod,
+          functionType: addUnusedMethod.getterType as ir.FunctionType)
+        ..fileOffset = node.fileOffset;
+    }
   }
 
   @override

pkg/kernel/lib/library_index.dart

@@ -123,6 +123,11 @@ class LibraryIndex {
     return _getLibraryIndex(library).getProcedure(containerName, memberName);
   }
 
+  Procedure? tryGetProcedure(
+      String library, String containerName, String memberName) {
+    return _getLibraryIndex(library).tryGetProcedure(containerName, memberName);
+  }
+
   Field getField(String library, String containerName, String memberName) {
     return _getLibraryIndex(library).getField(containerName, memberName);
   }
@@ -225,6 +230,10 @@ class _ContainerTable {
     return _getContainerIndex(className).getProcedure(memberName);
   }
 
+  Procedure? tryGetProcedure(String className, String memberName) {
+    return _getContainerIndex(className).tryGetProcedure(memberName);
+  }
+
   Field getField(String className, String memberName) {
     return _getContainerIndex(className).getField(memberName);
   }
@@ -411,6 +420,16 @@ class _MemberTable {
     return member;
   }
 
+  Procedure? tryGetProcedure(String name) {
+    Member? member = members[name];
+    if (member == null) return null;
+    if (member is! Procedure) {
+      throw "Member '$name' in $containerName is not a Procedure: "
+          "${member} (${member.runtimeType}).";
+    }
+    return member;
+  }
+
   Field getField(String name) {
     Member member = getMember(name);
     if (member is! Field) {