[Mac] Adds accelerator for Emoji menu item.

Mac's default "Edit -> Emoji & Symbols" menu item accelerator
is specified as the accelerator for the (MacViews) context menu item.

Bug: 827404
Change-Id: Ia030d6d0acebcb8481b39eea6c659f6855f6e5ab
Reviewed-on: https://chromium-review.googlesource.com/1011240
Commit-Queue: Ramya Nagarajan <ramyan@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#550871}(cherry picked from commit 5cefa30)
Reviewed-on: https://chromium-review.googlesource.com/1014507
Cr-Commit-Position: refs/branch-heads/3396@{#56}
Cr-Branched-From: 9ef2aa8-refs/heads/master@{#550428}

ui/views/controls/textfield/textfield.cc

@@ -1373,6 +1373,15 @@ bool Textfield::GetAcceleratorForCommandId(int command_id,
       *accelerator = ui::Accelerator(ui::VKEY_A, kPlatformModifier);
       return true;
 
+    case IDS_CONTENT_CONTEXT_EMOJI:
+#if defined(OS_MACOSX)
+      *accelerator = ui::Accelerator(ui::VKEY_SPACE,
+                                     ui::EF_COMMAND_DOWN | ui::EF_CONTROL_DOWN);
+      return true;
+#else
+      return false;
+#endif
+
     default:
       return false;
   }