Setup local var descriptors in kernel mode.

Closes https://github.com/dart-lang/sdk/issues/28054

R=kmillikin@google.com

Review-Url: https://codereview.chromium.org/2589733002 .

runtime/vm/compiler.cc

@@ -1593,8 +1593,12 @@ void Compiler::ComputeLocalVarDescriptors(const Code& code) {
   // if state changed while compiling in background.
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
-    Parser::ParseFunction(parsed_function);
-    parsed_function->AllocateVariables();
+    if (function.kernel_function() == NULL) {
+      Parser::ParseFunction(parsed_function);
+      parsed_function->AllocateVariables();
+    } else {
+      parsed_function->EnsureKernelScopes();
+    }
     const LocalVarDescriptors& var_descs = LocalVarDescriptors::Handle(
         parsed_function->node_sequence()->scope()->GetVarDescriptors(function));
     ASSERT(!var_descs.IsNull());

runtime/vm/kernel_to_il.cc

@@ -662,7 +662,7 @@ void ScopeBuilder::VisitFunctionNode(FunctionNode* node) {
     node->body()->AcceptStatementVisitor(this);
   }
 
-  // Ensure that :await_jump_var and :await_ctx_var are captured.
+  // Ensure that :await_jump_var, :await_ctx_var and :async_op are captured.
   if (node->async_marker() == FunctionNode::kSyncYielding) {
     {
       LocalVariable* temp = NULL;
@@ -676,6 +676,13 @@ void ScopeBuilder::VisitFunctionNode(FunctionNode* node) {
           (depth_.function_ == 0) ? &result_->yield_context_variable : &temp,
           Symbols::AwaitContextVar());
     }
+    {
+      LocalVariable* temp =
+          scope_->LookupVariable(Symbols::AsyncOperation(), true);
+      if (temp != NULL) {
+        scope_->CaptureVariable(temp);
+      }
+    }
   }
 }
 

runtime/vm/object.cc

@@ -13822,9 +13822,6 @@ RawLocalVarDescriptors* Code::GetLocalVarDescriptors() const {
   if (v.IsNull()) {
     ASSERT(!is_optimized());
     const Function& f = Function::Handle(function());
-    if (f.kernel_function() != NULL) {
-      return v.raw();
-    }
     ASSERT(!f.IsIrregexpFunction());  // Not yet implemented.
     Compiler::ComputeLocalVarDescriptors(*this);
   }