Revert two Kernel changes that were causing test failures.

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 551c0dd46cd21d12ef67d3c0c1bc257439c838f8..be7196884cb58264ba32f2d44c93b8db0fc588a7 100644
--- a/runtime/vm/kernel_binary_flowgraph.h
+++ b/runtime/vm/kernel_binary_flowgraph.h
@@ -860,7 +860,6 @@ class FieldHelper {
     kParentClassBinaryOffset,
     kName,
     kSourceUriIndex,
-    kDocumentationCommentIndex,
     kAnnotations,
     kType,
     kInitializer,
@@ -920,9 +919,6 @@ 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) {
@@ -1013,7 +1009,6 @@ class ProcedureHelper {
     kParentClassBinaryOffset,
     kName,
     kSourceUriIndex,
-    kDocumentationCommentIndex,
     kAnnotations,
     kFunction,
     kEnd
@@ -1068,9 +1063,6 @@ 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) {
@@ -1137,7 +1129,6 @@ class ConstructorHelper {
     kFlags,
     kParentClassBinaryOffset,
     kName,
-    kDocumentationCommentIndex,
     kAnnotations,
     kFunction,
     kInitializers,
@@ -1183,9 +1174,6 @@ 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) {