Add Member.documentationComment and use it to resynthesize documentation from Kernel.

pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
index 1bce990241a61b97bfc944e19630fefc6243730c..fadda95d116b6ad8cc5a57b8fb896842d5aeccd4 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_enum_builder.dart
@@ -125,10 +125,11 @@ class KernelEnumBuilder extends SourceClassBuilder
     ///       static const List<E> values = const <E>[id0, ..., idn-1];
     ///       String toString() => { 0: ‘E.id0’, . . ., n-1: ‘E.idn-1’}[index]
     ///     }
-    members["index"] = new KernelFieldBuilder(
-        null, intType, "index", finalMask, parent, charOffset, null, true);
+    members["index"] = new KernelFieldBuilder(null, null, intType, "index",
+        finalMask, parent, charOffset, null, true);
     KernelConstructorBuilder constructorBuilder = new KernelConstructorBuilder(
         null,
+        null,
         constMask,
         null,
         "",
@@ -144,11 +145,20 @@ class KernelEnumBuilder extends SourceClassBuilder
     constructors[""] = constructorBuilder;
     int index = 0;
     List<MapEntry> toStringEntries = <MapEntry>[];
-    KernelFieldBuilder valuesBuilder = new KernelFieldBuilder(null, listType,
-        "values", constMask | staticMask, parent, charOffset, null, true);
+    KernelFieldBuilder valuesBuilder = new KernelFieldBuilder(
+        null,
+        null,
+        listType,
+        "values",
+        constMask | staticMask,
+        parent,
+        charOffset,
+        null,
+        true);
     members["values"] = valuesBuilder;
     KernelProcedureBuilder toStringBuilder = new KernelProcedureBuilder(
         null,
+        null,
         0,
         stringType,
         "toString",
@@ -178,8 +188,16 @@ class KernelEnumBuilder extends SourceClassBuilder
         constantNamesAndOffsets[i] = null;
         continue;
       }
-      KernelFieldBuilder fieldBuilder = new KernelFieldBuilder(null, selfType,
-          name, constMask | staticMask, parent, charOffset, null, true);
+      KernelFieldBuilder fieldBuilder = new KernelFieldBuilder(
+          null,
+          null,
+          selfType,
+          name,
+          constMask | staticMask,
+          parent,
+          charOffset,
+          null,
+          true);
       members[name] = fieldBuilder;
       toStringEntries.add(new MapEntry(
           new IntLiteral(index), new StringLiteral("$className.$name")));