[test fixlet] Add tests for the zoom icon in the location bar on GTK.

chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm

Index: chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
diff --git a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
index be6d7f15e628417447db5373b5f6da3c24d04c4f..6ab404a1b03a045a0d9c52aa6ccf6bb9cdc5541e 100644
--- a/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
+++ b/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
@@ -48,6 +48,7 @@
 #import "chrome/browser/ui/cocoa/location_bar/web_intents_button_decoration.h"
 #import "chrome/browser/ui/cocoa/location_bar/zoom_decoration.h"
 #import "chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.h"
+#import "chrome/browser/ui/cocoa/view_id_util.h"
 #include "chrome/browser/ui/content_settings/content_setting_bubble_model.h"
 #include "chrome/browser/ui/content_settings/content_setting_image_model.h"
 #include "chrome/browser/ui/intents/web_intent_picker_controller.h"
@@ -116,6 +117,7 @@ LocationBarViewMac::LocationBarViewMac(
           content::PAGE_TRANSITION_TYPED |
           content::PAGE_TRANSITION_FROM_ADDRESS_BAR)),
       weak_ptr_factory_(this) {
+  view_id_util::SetID(zoom_decoration_, VIEW_ID_ZOOM_BUTTON);
   if (extensions::switch_utils::IsActionBoxEnabled()) {
     plus_decoration_.reset(new PlusDecoration(this, browser_));
   }