NeedsManualRebaseline for async/await stack trace test

third_party/WebKit/LayoutTests/TestExpectations

 # Intentional failures to test the layout test system.
 Bug(intentional) [ Android Linux Win Mac10.10 Mac10.11 Retina ] harness-tests/crash.html [ Crash ]
 crbug.com/644303 [ Mac10.9 ] harness-tests/crash.html [ Crash Timeout ]
 Bug(intentional) harness-tests/timeout.html [ Timeout ]
 
 # ====== Oilpan-only failures from here ======
 # Most of these actually cause the tests to report success, rather than
 # failure. Expected outputs will be adjusted for the better once Oilpan
 # has been well and truly enabled always.
 
@@ skipping 542 matching lines @@
 
 # These tests pass but images do not match because of wrong half-leading in vertical-lr
 crbug.com/537080 imported/csswg-test/css-writing-modes-3/vertical-alignment-003.xht [ Failure ]
 crbug.com/537080 imported/csswg-test/css-writing-modes-3/vertical-alignment-009.xht [ Failure ]
 
 # These tests fail / timeout until https://www.chromestatus.com/features/5643236399906816 ships
 crbug.com/621515 inspector/sources/debugger-async/async-await/async-callstack-async-await1.html [ Skip ]
 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 ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vlr-005.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vlr-007.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vlr-009.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vrl-002.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vrl-004.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vrl-006.xht [ Failure ]
 crbug.com/492664 imported/csswg-test/css-writing-modes-3/clip-rect-vrl-008.xht [ Failure ]
@@ skipping 676 matching lines @@
 # this tested without the feature by using the virtual test. See
 # virtual/stable/http/tests/navigation/beacon-cross-origin-redirect-blob-expected.txt
 crbug.com/490015 http/tests/navigation/beacon-cross-origin-redirect-blob.html [ Skip ]
 # This test doesn't need to be run with the stable release mode.
 crbug.com/490015 virtual/stable/http/tests/navigation/beacon-blob-with-non-simple-type.html [ Skip ]
 # This test fails with the stable release mode.
 crbug.com/490015 virtual/stable/http/tests/navigation/same-and-different-back.html [ Skip ]
 
 # Tests added from W3C auto import bot
 crbug.com/626703 [ Win10 ] imported/csswg-test/vendor-imports/mozilla/mozilla-central-reftests/flexbox/flexbox-baseline-align-self-baseline-vert-001.html [ Failure ]