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

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

Index: pkg/front_end/lib/src/fasta/kernel/kernel_procedure_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_procedure_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_procedure_builder.dart
index 27d69152aaec93f9db813f856a41a7b87e9819b6..5da69b667122d097700b568ebf3f0fc80553e1bd 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_procedure_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_procedure_builder.dart
@@ -81,6 +81,7 @@ abstract class KernelFunctionBuilder
   Statement actualBody;
 
   KernelFunctionBuilder(
+      String documentationComment,
       List<MetadataBuilder> metadata,
       int modifiers,
       KernelTypeBuilder returnType,
@@ -90,8 +91,8 @@ abstract class KernelFunctionBuilder
       KernelLibraryBuilder compilationUnit,
       int charOffset,
       this.nativeMethodName)
-      : super(metadata, modifiers, returnType, name, typeVariables, formals,
-            compilationUnit, charOffset);
+      : super(documentationComment, metadata, modifiers, returnType, name,
+            typeVariables, formals, compilationUnit, charOffset);
 
   void set body(Statement newBody) {
     if (newBody != null) {
@@ -207,6 +208,7 @@ class KernelProcedureBuilder extends KernelFunctionBuilder {
   final ConstructorReferenceBuilder redirectionTarget;
 
   KernelProcedureBuilder(
+      String documentationComment,
       List<MetadataBuilder> metadata,
       int modifiers,
       KernelTypeBuilder returnType,
@@ -224,8 +226,17 @@ class KernelProcedureBuilder extends KernelFunctionBuilder {
             fileUri: compilationUnit?.relativeFileUri)
           ..fileOffset = charOffset
           ..fileEndOffset = charEndOffset,
-        super(metadata, modifiers, returnType, name, typeVariables, formals,
-            compilationUnit, charOffset, nativeMethodName);
+        super(
+            documentationComment,
+            metadata,
+            modifiers,
+            returnType,
+            name,
+            typeVariables,
+            formals,
+            compilationUnit,
+            charOffset,
+            nativeMethodName);
 
   ProcedureKind get kind => procedure.kind;
 
@@ -276,6 +287,7 @@ class KernelProcedureBuilder extends KernelFunctionBuilder {
       procedure.isExternal = isExternal;
       procedure.isConst = isConst;
       procedure.name = new Name(name, library.target);
+      procedure.documentationComment = documentationComment;
     }
     if (isEligibleForTopLevelInference) {
       library.loader.typeInferenceEngine.recordMember(procedure);
@@ -310,6 +322,7 @@ class KernelConstructorBuilder extends KernelFunctionBuilder {
   RedirectingInitializer redirectingInitializer;
 
   KernelConstructorBuilder(
+      String documentationComment,
       List<MetadataBuilder> metadata,
       int modifiers,
       KernelTypeBuilder returnType,
@@ -324,8 +337,17 @@ class KernelConstructorBuilder extends KernelFunctionBuilder {
       : constructor = new Constructor(null)
           ..fileOffset = charOffset
           ..fileEndOffset = charEndOffset,
-        super(metadata, modifiers, returnType, name, typeVariables, formals,
-            compilationUnit, charOffset, nativeMethodName);
+        super(
+            documentationComment,
+            metadata,
+            modifiers,
+            returnType,
+            name,
+            typeVariables,
+            formals,
+            compilationUnit,
+            charOffset,
+            nativeMethodName);
 
   bool get isInstanceMember => false;
 
@@ -348,6 +370,7 @@ class KernelConstructorBuilder extends KernelFunctionBuilder {
       constructor.isConst = isConst;
       constructor.isExternal = isExternal;
       constructor.name = new Name(name, library.target);
+      constructor.documentationComment = documentationComment;
     }
     return constructor;
   }