Reproduction steps:

1. Launch Chrome from the command line with a fresh profile.
2. Try to sign in using the profile button.
3. After entering an email address, the window switches to a view that prompts for a password. At the same time, we see in the console:

""""
Dec 27 15:37:08  Chromium Helper[83955] <Warning>: CGSConnectionByID: 0 is not a valid connection ID.
Dec 27 15:37:08  Chromium Helper[83955] <Warning>: Invalid Connection ID 0
"""

Using lldb to break at the address where the log is emitted shows:
"""
 * frame #0: 0x00007fff8b2e6d4b CoreGraphics`CGSConnectionByID
    frame #1: 0x00007fff8b2e7a39 CoreGraphics`CGSGetConnectionPortById + 14
    frame #2: 0x00007fff8b72fded CoreGraphics`CGSSetSecureEventInput + 16
    frame #3: 0x00007fff9cecbad8 HIToolbox`EnableSecureEventInput + 40
    frame #4: 0x000000012fdcabaf libblink_platform.dylib`enableSecureTextInput + 31 at SecureTextInput.cpp:36
    frame #5: 0x00000001340999a3 libblink_core.dylib`setUseSecureKeyboardEntry + 35 at FrameSelection.cpp:1016
    frame #6: 0x0000000134099a1b libblink_core.dylib`updateSecureKeyboardEntryIfActive + 59 at FrameSelection.cpp:1003
    frame #7: 0x0000000134099a7d libblink_core.dylib`setUseSecureKeyboardEntryWhenActive + 77 at FrameSelection.cpp:1011
    frame #8: 0x0000000134688fdf libblink_core.dylib`enableSecureTextInput + 79 at PasswordInputType.cpp:83
    frame #9: 0x00000001345237d1 libblink_core.dylib`handleFocusEvent + 113 at HTMLInputElement.cpp:349
    frame #10: 0x000000013460c03b libblink_core.dylib`dispatchFocusEvent + 91 at TextControlElement.cpp:96
    frame #11: 0x0000000134f741e5 libblink_core.dylib`dispatchFocusEvent + 53 at FocusController.cpp:350
    frame #12: 0x0000000134f74afe libblink_core.dylib`dispatchEventsOnWindowAndFocusedElement + 622 at FocusController.cpp:386
    frame #13: 0x0000000134f7487d libblink_core.dylib`setFocused + 429 at FocusController.cpp:866
    frame #14: 0x00000001320b74e4 libblink_web.dylib`setFocus + 100 at WebViewImpl.cpp:2253
    frame #15: 0x00000001320a31c2 libblink_web.dylib`setFocus + 50 at WebViewFrameWidget.cpp:115
    frame #16: 0x00000001204a0e28 libcontent.dylib`OnSetFocus + 120 at render_widget.cc:819
    frame #17: 0x0000000120483d25 libcontent.dylib`SetFocus + 37 at render_view_impl.cc:2435
    frame #18: 0x0000000120483cd0 libcontent.dylib`OnSetFocus + 240 at render_view_impl.cc:2431
    frame #19: 0x00000001204b2752 libcontent.dylib`DispatchToMethodImpl<content::RenderWidget *, void (content::RenderWidget::*)(bool), const std::__1::tuple<bool> &, 0> + 162 at tuple.h:91
    frame #20: 0x00000001204b26a0 libcontent.dylib`DispatchToMethod<content::RenderWidget *, void (content::RenderWidget::*)(bool), const std::__1::tuple<bool> &> + 96 at tuple.h:98
    frame #21: 0x00000001204b261d libcontent.dylib`DispatchToMethod<content::RenderWidget, void (content::RenderWidget::*)(bool), void, std::__1::tuple<bool> > + 109 at ipc_message_templates.h:26
    frame #22: 0x000000012049b55f libcontent.dylib`Dispatch<content::RenderWidget, content::RenderWidget, void, void (content::RenderWidget::*)(bool)> + 479 at ipc_message_templates.h:121
    frame #23: 0x0000000120498cba libcontent.dylib`OnMessageReceived + 2682 at render_widget.cc:605
    frame #24: 0x000000012047393e libcontent.dylib`OnMessageReceived + 9102 at render_view_impl.cc:1265
"""

Note that this error goes away when we run Chrome with "--no-sandbox". Over to rsesek to investigate further.