NeedsManualRebaseline for async/await stack trace test

third_party/WebKit/LayoutTests/TestExpectations

Index: third_party/WebKit/LayoutTests/TestExpectations
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index 171c43f051a64f69bf3711bd3acb3c3674b5f3d8..5fb7b0a6e4ca580b14bdfda4549dd1872df0f50a 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -560,6 +560,9 @@ crbug.com/621515 inspector/sources/debugger-async/async-await/async-callstack-as
 crbug.com/621515 inspector/sources/debugger-async/async-await/async-callstack-async-await2.html [ Skip ]
 crbug.com/621515 inspector/sources/debugger-async/async-await/async-callstack-async-await3.html [ Skip ]
 
+# Stack traces for async functions are improving as the desugaring changes
+crbug.com/646199 virtual/asyncawait/inspector/sources/debugger-async/async-await/async-callstack-async-await3.html [ NeedsManualRebaseline ]
+
 # These tests pass but images do not match because of position: absolute in vertical flow bug
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/block-flow-direction-vrl-009.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vlr-003.xht [ Failure ]