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

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

 // Copyright (c) 2012 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.
 
 #import "chrome/browser/ui/cocoa/location_bar/zoom_decoration.h"
 
 #include "base/string16.h"
 #include "base/string_number_conversions.h"
 #include "chrome/app/chrome_command_ids.h"
 #import "chrome/browser/ui/cocoa/omnibox/omnibox_view_mac.h"
+#import "chrome/browser/ui/cocoa/view_id_util.h"
 #include "chrome/browser/ui/toolbar/toolbar_model.h"
 #include "chrome/browser/ui/zoom/zoom_controller.h"
 #include "grit/generated_resources.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
 ZoomDecoration::ZoomDecoration(ToolbarModel* toolbar_model)
     : toolbar_model_(toolbar_model) {
   Update(NULL);
 }
 
 ZoomDecoration::~ZoomDecoration() {
 }
 
 void ZoomDecoration::Update(ZoomController* zoom_controller) {
   if (!zoom_controller || zoom_controller->IsAtDefaultZoom() ||
       toolbar_model_->input_in_progress()) {
     // TODO(dbeam): hide zoom bubble when it exists.
     SetVisible(false);
     return;
   }
 
   SetImage(OmniboxViewMac::ImageForResource(
       zoom_controller->GetResourceForZoomLevel()));
+  view_id_util::SetID(GetImage(), VIEW_ID_ZOOM_BUTTON);
 
   string16 zoom_percent = base::IntToString16(zoom_controller->zoom_percent());
   NSString* zoom_string =
       l10n_util::GetNSStringFWithFixup(IDS_TOOLTIP_ZOOM, zoom_percent);
   tooltip_.reset([zoom_string retain]);
 
   SetVisible(true);
 }
 
 bool ZoomDecoration::AcceptsMousePress() {
   return true;
 }
 
 NSString* ZoomDecoration::GetToolTip() {
   return tooltip_.get();
 }