Re-add backspace-goes-back as a default disabled finch trial

chrome/browser/global_keyboard_shortcuts_mac_unittest.mm

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <AppKit/NSEvent.h>
 #include <Carbon/Carbon.h>
 #include <stddef.h>
 
 #include "chrome/browser/global_keyboard_shortcuts_mac.h"
 
@@ skipping 11 matching lines @@
   const KeyboardShortcutData *it =
       GetWindowKeyboardShortcutTable(&num_shortcuts);
   ASSERT_GT(num_shortcuts, 0U);
   for (size_t i = 0; i < num_shortcuts; ++i, ++it) {
     int cmd_num = CommandForWindowKeyboardShortcut(
         it->command_key, it->shift_key, it->cntrl_key, it->opt_key,
         it->vkey_code, it->key_char);
     EXPECT_EQ(cmd_num, it->chrome_command);
   }
 
-  // Test that cmd-left is not a window-level command (else it
-  // would be invoked even if e.g. the omnibox had focus, where it really
+  // Test that cmd-left and backspace are not window-level commands (else they
+  // would be invoked even if e.g. the omnibox had focus, where they really
   // should have text editing functionality).
   EXPECT_EQ(-1, CommandForWindowKeyboardShortcut(
       true, false, false, false, kVK_LeftArrow, 0));
+  EXPECT_EQ(-1, CommandForWindowKeyboardShortcut(
+      false, false, false, false, kVK_Delete, 0));
 
   // Test that Cmd-'{' and Cmd-'}' are interpreted as IDC_SELECT_NEXT_TAB
   // and IDC_SELECT_PREVIOUS_TAB regardless of the virtual key code values.
   EXPECT_EQ(IDC_SELECT_NEXT_TAB, CommandForWindowKeyboardShortcut(
       true, false, false, false, kVK_ANSI_Period, '}'));
   EXPECT_EQ(IDC_SELECT_PREVIOUS_TAB, CommandForWindowKeyboardShortcut(
       true, true, false, false, kVK_ANSI_Slash, '{'));
 
   // One more test for Cmd-'{' / Alt-8 (on German keyboard layout).
   EXPECT_EQ(IDC_SELECT_PREVIOUS_TAB, CommandForWindowKeyboardShortcut(
@@ skipping 138 matching lines @@
   // cmd-shift-'[' in an RTL context pre 10.9.
   EXPECT_EQ('{', KeyCharacterForEvent(
       KeyEvent(true,  true,  false, false, @"{", @"}")));
   // cmd-shift-'[' in an RTL context on 10.9.
   EXPECT_EQ('{', KeyCharacterForEvent(
       KeyEvent(true,  true,  false, false, @"[", @"}")));
   // Test if getting dead-key events return 0 and do not hang.
   EXPECT_EQ(0,   KeyCharacterForEvent(
       KeyEvent(false, false, false, false, @"",  @"")));
 }