Bubble up exceptions throw async/await.

runtime/vm/parser.h

Index: runtime/vm/parser.h
diff --git a/runtime/vm/parser.h b/runtime/vm/parser.h
index 3fcf646e37d5fe05f65def6416087b6ee725a55c..2edc19a8b0084dbb630a4c97f34c1a700977ec3d 100644
--- a/runtime/vm/parser.h
+++ b/runtime/vm/parser.h
@@ -543,10 +543,12 @@ class Parser : public ValueObject {
   void OpenFunctionBlock(const Function& func);
   void OpenAsyncClosure();
   RawFunction* OpenAsyncFunction(intptr_t formal_param_pos);
+  void OpenAsyncTryBlock();
   SequenceNode* CloseBlock();
   SequenceNode* CloseAsyncFunction(const Function& closure,
                                    SequenceNode* closure_node);
-  void CloseAsyncClosure(SequenceNode* body);
+  SequenceNode* CloseAsyncClosure(SequenceNode* body);
+  SequenceNode* CloseAsyncTryBlock(SequenceNode* try_block);
   void AddAsyncClosureVariables();