Don't inline functions that the parser decides shouldn't be inlined.

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
diff --git a/runtime/vm/flow_graph_inliner.cc b/runtime/vm/flow_graph_inliner.cc
index f07e7cd1f2e5bf0cf2591d91301594b0fa571be5..a19916150d304af5ab7c7d6f5bea78d31317fb97 100644
--- a/runtime/vm/flow_graph_inliner.cc
+++ b/runtime/vm/flow_graph_inliner.cc
@@ -780,8 +780,15 @@ class CallSiteInliner : public ValueObject {
         {
           CSTAT_TIMER_SCOPE(thread(), graphinliner_parse_timer);
           parsed_function = GetParsedFunction(function, &in_cache);
+          if (!function.CanBeInlined()) {
+            // As a side effect of parsing the function, it may be marked

[Kevin Millikin (Google), 2017/02/24 14:32:28]

We already know whether the function is async or async* (when we created it), so
we shouldn't need to parse it.  I suggest marking async and async* functions not
inlinable at the same time that their modifier is set and letting the earlier
CanBeInlined() test in this method catch them without going through all the
other work.

+            // as not inlinable. This happens for async and async* functions
+            // when causal stack traces are being tracked.
+            return false;
+          }
         }
 
+
         // Build the callee graph.
         InlineExitCollector* exit_collector =
             new (Z) InlineExitCollector(caller_graph_, call);