Revert "macOS: Display [ctr + tab] and [ctr + shift + tab] as hotkeys for tab switching."

This reverts commit c93c3dca594c13251590042f228f8a1029eca985.

Reason for revert: Suspect this caused a crash on 10.13 (dbg): https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.13%20Tests%20%28dbg%29/3973

Original change's description:
> macOS: Display [ctr + tab] and [ctr + shift + tab] as hotkeys for tab switching.
> 
> This matches other macOS application like Safari, Terminal, etc. All existing
> hotkeys will still work.
> 
> This CL uses the same hotkey for "previous tab" that Safari and Terminal use,
> which is [ctr + shift + "Horizontal Tab"]. This also causes tests to pass.
> However, pressing that key combination actually generates [ctr + shift + "End of
> Medium"], which renderers in the Main Menu as a backwards tab. This CL updates
> NSMenuItem(ChromeAdditions) to check for this special case.
> 
> This CL removes two incorrect DCHECKs from render_widget_host_view_cocoa.mm. I
> regularly hit both of them when running Chromium on a local build. They both
> rely on the false assumption that keyEquivalents in the main menu must have the
> command modifier.
> 
> Bug: 851714
> Change-Id: I90c643870f9bc7dd87369496eec9ab62a1685e07
> Reviewed-on: https://chromium-review.googlesource.com/1106659
> Commit-Queue: Erik Chen <erikchen@chromium.org>
> Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
> Reviewed-by: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#574211}

TBR=thakis@chromium.org,asvitkine@chromium.org,erikchen@chromium.org

Change-Id: I4ce9b2e4dac1f0f2fae815528a1523326ac1d134
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 851714
Reviewed-on: https://chromium-review.googlesource.com/1134098
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574311}
7 files changed