content_browsertests failing on chromium.mac/Mac10.12 Tests

Builders failed on: 
- Mac10.12 Tests: 
  https://build.chromium.org/p/chromium.mac/builders/Mac10.12%20Tests


[ RUN      ] DumpAccessibilityTreeTest.AccessibilityModalDialogInIframeClosed
[83975:33539:0630/100216.248642:23657350815635:ERROR:devtools_http_handler.cc(787)]
DevTools listening on 127.0.0.1:58692
[83975:775:0630/100216.572649:23657674815755:INFO:dump_accessibility_browsertest_base.cc(234)] Testing: /b/s/w/ir/content/test/data/accessibility/html/modal-dialog-in-iframe-closed.html
[83975:775:0630/100216.572748:23657674910907:INFO:dump_accessibility_browsertest_base.cc(236)] Expected output: /b/s/w/ir/content/test/data/accessibility/html/modal-dialog-in-iframe-closed-expected-blink.txt
[83975:775:0630/100216.671920:23657774086447:INFO:dump_accessibility_browsertest_base.cc(402)] Test output matches expectations.
[83975:775:0630/100216.679015:23657781179302:INFO:dump_accessibility_browsertest_base.cc(234)] Testing: /b/s/w/ir/content/test/data/accessibility/html/modal-dialog-in-iframe-closed.html
[83975:775:0630/100216.679069:23657781229073:INFO:dump_accessibility_browsertest_base.cc(236)] Expected output: /b/s/w/ir/content/test/data/accessibility/html/modal-dialog-in-iframe-closed-expected-mac.txt
../../content/browser/accessibility/dump_accessibility_browsertest_base.cc:365: Failure
Value of: is_different
  Actual: true
Expected: false
[83975:775:0630/100216.749474:23657851639864:ERROR:dump_accessibility_browsertest_base.cc(390)] Diff:
* Line Expected
- ---- --------
     1 AXWebArea
     2 ++AXGroup
     3 ++++AXStaticText AXValue='Test for modal dialog closed in an iframe. '
     4 ++++AXGroup
*    5 ++++++AXWebArea
     6 ++++++++AXGroup
     7 ++++++++++AXButton AXTitle='I am a non-inert button!'
     8 <-- End-of-file -->
Actual
------
AXWebArea
++AXGroup
++++AXStaticText AXValue='Test for modal dialog closed in an iframe. '
++++AXGroup
<-- End-of-file -->
[  FAILED  ] DumpAccessibilityTreeTest.AccessibilityModalDialogInIframeClosed, where TypeParam =  and GetParam() =  (638 ms)