Track the 'awaiter return' call stack use it to detect uncaught exceptions in async functions

runtime/vm/code_descriptors.h

Index: runtime/vm/code_descriptors.h
diff --git a/runtime/vm/code_descriptors.h b/runtime/vm/code_descriptors.h
index 2500ed808d9b4ed161494d3145f11a6a204cbb63..5a1528e174c0317a8659752016f9827bb46d4181 100644
--- a/runtime/vm/code_descriptors.h
+++ b/runtime/vm/code_descriptors.h
@@ -74,6 +74,8 @@ class ExceptionHandlerList : public ZoneAllocated {
   struct HandlerDesc {
     intptr_t outer_try_index;    // Try block in which this try block is nested.
     intptr_t pc_offset;          // Handler PC offset value.
+    TokenPosition token_pos;     // Token position of handler.
+    bool is_generated;           // False if this is directly from Dart code.
     const Array* handler_types;  // Catch clause guards.
     bool needs_stacktrace;
   };
@@ -86,6 +88,8 @@ class ExceptionHandlerList : public ZoneAllocated {
     struct HandlerDesc data;
     data.outer_try_index = -1;
     data.pc_offset = ExceptionHandlers::kInvalidPcOffset;
+    data.token_pos = TokenPosition::kNoSource;
+    data.is_generated = true;
     data.handler_types = NULL;
     data.needs_stacktrace = false;
     list_.Add(data);
@@ -94,6 +98,8 @@ class ExceptionHandlerList : public ZoneAllocated {
   void AddHandler(intptr_t try_index,
                   intptr_t outer_try_index,
                   intptr_t pc_offset,
+                  TokenPosition token_pos,
+                  bool is_generated,
                   const Array& handler_types,
                   bool needs_stacktrace) {
     ASSERT(try_index >= 0);
@@ -103,6 +109,8 @@ class ExceptionHandlerList : public ZoneAllocated {
     list_[try_index].outer_try_index = outer_try_index;
     ASSERT(list_[try_index].pc_offset == ExceptionHandlers::kInvalidPcOffset);
     list_[try_index].pc_offset = pc_offset;
+    list_[try_index].token_pos = token_pos;
+    list_[try_index].is_generated = is_generated;
     ASSERT(handler_types.IsZoneHandle());
     list_[try_index].handler_types = &handler_types;
     list_[try_index].needs_stacktrace |= needs_stacktrace;