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

runtime/vm/kernel_binary_flowgraph.h

Index: runtime/vm/kernel_binary_flowgraph.h
diff --git a/runtime/vm/kernel_binary_flowgraph.h b/runtime/vm/kernel_binary_flowgraph.h
index be7196884cb58264ba32f2d44c93b8db0fc588a7..551c0dd46cd21d12ef67d3c0c1bc257439c838f8 100644
--- a/runtime/vm/kernel_binary_flowgraph.h
+++ b/runtime/vm/kernel_binary_flowgraph.h
@@ -860,6 +860,7 @@ class FieldHelper {
     kParentClassBinaryOffset,
     kName,
     kSourceUriIndex,
+    kDocumentationCommentIndex,
     kAnnotations,
     kType,
     kInitializer,
@@ -919,6 +920,9 @@ class FieldHelper {
         builder_->record_token_position(position_);
         builder_->record_token_position(end_position_);
         if (++next_read_ == field) return;
+      case kDocumentationCommentIndex:
+        builder_->ReadStringReference();
+        if (++next_read_ == field) return;
       case kAnnotations: {
         annotation_count_ = builder_->ReadListLength();  // read list length.
         for (intptr_t i = 0; i < annotation_count_; ++i) {
@@ -1009,6 +1013,7 @@ class ProcedureHelper {
     kParentClassBinaryOffset,
     kName,
     kSourceUriIndex,
+    kDocumentationCommentIndex,
     kAnnotations,
     kFunction,
     kEnd
@@ -1063,6 +1068,9 @@ class ProcedureHelper {
         builder_->record_token_position(position_);
         builder_->record_token_position(end_position_);
         if (++next_read_ == field) return;
+      case kDocumentationCommentIndex:
+        builder_->ReadStringReference();
+        if (++next_read_ == field) return;
       case kAnnotations: {
         annotation_count_ = builder_->ReadListLength();  // read list length.
         for (intptr_t i = 0; i < annotation_count_; ++i) {
@@ -1129,6 +1137,7 @@ class ConstructorHelper {
     kFlags,
     kParentClassBinaryOffset,
     kName,
+    kDocumentationCommentIndex,
     kAnnotations,
     kFunction,
     kInitializers,
@@ -1174,6 +1183,9 @@ class ConstructorHelper {
       case kName:
         builder_->SkipName();  // read name.
         if (++next_read_ == field) return;
+      case kDocumentationCommentIndex:
+        builder_->ReadStringReference();
+        if (++next_read_ == field) return;
       case kAnnotations: {
         annotation_count_ = builder_->ReadListLength();  // read list length.
         for (intptr_t i = 0; i < annotation_count_; ++i) {