Suspect efd05aec93fad28adb8bef9674530e7bbe64766f causes the test to fail in a flaky manner. FindIt is 77% confident that this change introduces the issue, and this seems reasonable from the CL description.

Proceeding with revert.

Retrying 1 test (retry #1)
[ RUN      ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting
2017-01-20 14:47:46.158 interactive_ui_tests[6358:41439] NSWindow warning: adding an unknown subview: <FullSizeContentView: 0x7f8c886d0ea0>
2017-01-20 14:47:46.159 interactive_ui_tests[6358:41439] Call stack:
(
    "+callStackSymbols disabled for performance reasons"
)
[6358:779:0120/144746.921457:WARNING:render_frame_host_impl.cc(2155)] OnDidStopLoading was called twice.
[6358:93703:0120/144746.960896:WARNING:embedded_test_server.cc(219)] Request not handled. Returning 404: /favicon.ico
../../chrome/browser/site_per_process_interactive_browsertest.cc:171: Failure
Value of: result
  Actual: ""
Expected: "FOO"
[  FAILED  ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting, where TypeParam =  and GetParam() =  (1341 ms)
[385/385] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting (1583 ms)
Retrying 1 test (retry #2)
[ RUN      ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting
2017-01-20 14:47:47.760 interactive_ui_tests[6366:41551] NSWindow warning: adding an unknown subview: <FullSizeContentView: 0x7fec405f6f70>
2017-01-20 14:47:47.760 interactive_ui_tests[6366:41551] Call stack:
(
    "+callStackSymbols disabled for performance reasons"
)
[6366:779:0120/144748.519196:WARNING:render_frame_host_impl.cc(2155)] OnDidStopLoading was called twice.
[6366:93703:0120/144748.560899:WARNING:embedded_test_server.cc(219)] Request not handled. Returning 404: /favicon.ico
../../chrome/browser/site_per_process_interactive_browsertest.cc:171: Failure
Value of: result
  Actual: "F"
Expected: "FOO"
[  FAILED  ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting, where TypeParam =  and GetParam() =  (1366 ms)
[386/386] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting (1587 ms)
Retrying 1 test (retry #3)
[ RUN      ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting
2017-01-20 14:47:49.349 interactive_ui_tests[6376:41667] NSWindow warning: adding an unknown subview: <FullSizeContentView: 0x7fed01f60950>
2017-01-20 14:47:49.349 interactive_ui_tests[6376:41667] Call stack:
(
    "+callStackSymbols disabled for performance reasons"
)
[6376:779:0120/144750.233747:WARNING:render_frame_host_impl.cc(2155)] OnDidStopLoading was called twice.
[6376:94475:0120/144750.283376:WARNING:embedded_test_server.cc(219)] Request not handled. Returning 404: /favicon.ico
../../chrome/browser/site_per_process_interactive_browsertest.cc:171: Failure
Value of: result
  Actual: "F"
Expected: "FOO"
[  FAILED  ] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting, where TypeParam =  and GetParam() =  (1583 ms)
[387/387] SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting (1848 ms)
1 test failed:
    SitePerProcessInteractiveBrowserTest.SubframeKeyboardEventRouting (../../chrome/browser/site_per_process_interactive_browsertest.cc:136)

Revert b5ac0ebfe4e03b8e1da707fa38f29550022a94ea appears to have fixed, at least on Linux Tests

 Issue 683419  has been merged into this issue.

 Issue 683440  has been merged into this issue.