Add Ctrl+Shift+Q exit accelerator back

Though the accelerator is now handled by ConfirmQuitBubbleController, we still
need the accelerator entry for showing the accelerator subtext in the menu on
the Exit entry.

BUG=859830
R=pkasting

Change-Id: Ia5f40482b009619d0cb44d5b05b9592b7fb13700
Reviewed-on: https://chromium-review.googlesource.com/1125082Reviewed-by: Peter Kasting <pkasting@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572370}

chrome/browser/ui/views/accelerator_table.cc

@@ -151,6 +151,7 @@ const AcceleratorMapping kAcceleratorMap[] = {
     {ui::VKEY_BROWSER_SEARCH, ui::EF_NONE, IDC_FOCUS_SEARCH},
     {ui::VKEY_M, ui::EF_SHIFT_DOWN | ui::EF_PLATFORM_ACCELERATOR,
      IDC_SHOW_AVATAR_MENU},
+    {ui::VKEY_Q, ui::EF_SHIFT_DOWN | ui::EF_CONTROL_DOWN, IDC_EXIT},
 #endif  // !OS_CHROMEOS
 
 #if defined(GOOGLE_CHROME_BUILD) && !defined(OS_MACOSX)