[Ash] Disallow calling HoverHighlightView::SetSubText() with an empty string

ash/system/tray/hover_highlight_view.cc

 // Copyright 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.
 
 #include "ash/system/tray/hover_highlight_view.h"
 
 #include "ash/resources/vector_icons/vector_icons.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_popup_utils.h"
 #include "ash/system/tray/tri_view.h"
@@ skipping 39 matching lines @@
 void HoverHighlightView::SetRightViewVisible(bool visible) {
   if (!right_view_)
     return;
 
   right_view_->SetVisible(visible);
   Layout();
 }
 
 void HoverHighlightView::SetSubText(const base::string16& sub_text) {
   DCHECK(text_label_);
+  DCHECK(!sub_text.empty());
 
   if (!sub_text_label_) {
     sub_text_label_ = TrayPopupUtils::CreateDefaultLabel();
     tri_view_->AddView(TriView::Container::CENTER, sub_text_label_);
   }
+
   TrayPopupItemStyle sub_style(TrayPopupItemStyle::FontStyle::CAPTION);
   sub_style.set_color_style(TrayPopupItemStyle::ColorStyle::INACTIVE);
   sub_style.SetupLabel(sub_text_label_);
   sub_text_label_->SetText(sub_text);
 }
 
 void HoverHighlightView::AddIconAndLabel(const gfx::ImageSkia& image,
                                          const base::string16& text) {
   DoAddIconAndLabel(image, text,
                     TrayPopupItemStyle::FontStyle::DETAILED_VIEW_LABEL);
@@ skipping 35 matching lines @@
   left_icon_->SetEnabled(enabled());
   tri_view_->AddView(TriView::Container::START, left_icon_);
 
   text_label_ = TrayPopupUtils::CreateDefaultLabel();
   text_label_->SetText(text);
   text_label_->SetEnabled(enabled());
   TrayPopupItemStyle style(font_style);
   style.SetupLabel(text_label_);
   tri_view_->AddView(TriView::Container::CENTER, text_label_);
 
-  SetSubText(sub_text);
+  if (!sub_text.empty())
+    SetSubText(sub_text);
 
   tri_view_->SetContainerVisible(TriView::Container::END, false);
 
   SetAccessibleName(text);
 }
 
 void HoverHighlightView::AddLabelRow(const base::string16& text) {
   SetLayoutManager(new views::FillLayout);
   tri_view_ = TrayPopupUtils::CreateDefaultRowView();
   AddChildView(tri_view_);
@@ skipping 67 matching lines @@
   if (right_view_)
     right_view_->SetEnabled(enabled());
 }
 
 void HoverHighlightView::OnFocus() {
   ScrollRectToVisible(gfx::Rect(gfx::Point(), size()));
   ActionableView::OnFocus();
 }
 
 }  // namespace ash