Update the bookmark tooltip text only when necessary

chrome/browser/ui/views/bookmarks/bookmark_bar_view.cc

 // 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.
 
 #include "chrome/browser/ui/views/bookmarks/bookmark_bar_view.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 239 matching lines @@
 class BookmarkButton : public BookmarkButtonBase {
  public:
   // The internal view class name.
   static const char kViewClassName[];
 
   BookmarkButton(views::ButtonListener* listener,
                  const GURL& url,
                  const base::string16& title)
       : BookmarkButtonBase(listener, title), url_(url) {}
 
+  // views::View:
   bool GetTooltipText(const gfx::Point& p,
-                      base::string16* tooltip) const override {
+                      base::string16* tooltip_text) const override {
+    const views::TooltipManager* tooltip_manager =
+        GetWidget()->GetTooltipManager();
     gfx::Point location(p);
     ConvertPointToScreen(this, &location);
-    *tooltip = BookmarkBarView::CreateToolTipForURLAndTitle(
-        GetWidget(), location, url_, GetText());
-    return !tooltip->empty();
+    // Also update when the maximum width for tooltip has changed because the
+    // it may be elided differently.
+    int max_tooltip_width = tooltip_manager->GetMaxWidth(location);
+    if (tooltip_text_.empty() || max_tooltip_width != max_tooltip_width_) {
+      max_tooltip_width_ = max_tooltip_width;
+      tooltip_text_ = BookmarkBarView::CreateToolTipForURLAndTitle(
+          max_tooltip_width_, tooltip_manager->GetFontList(), url_, GetText());
+    }
+    *tooltip_text = tooltip_text_;
+    return !tooltip_text->empty();
+  }
+
+  void SetText(const base::string16& text) override {
+    BookmarkButtonBase::SetText(text);
+    tooltip_text_.empty();
   }
 
   const char* GetClassName() const override { return kViewClassName; }
 
  private:
+  // A cached value of maximum width for tooltip to skip generating
+  // new tooltip text.
+  mutable int max_tooltip_width_ = 0;
+  mutable base::string16 tooltip_text_;
   const GURL& url_;
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkButton);
 };
 
 // static
 const char BookmarkButton::kViewClassName[] = "BookmarkButton";
 
 // ShortcutButton -------------------------------------------------------------
 
@@ skipping 420 matching lines @@
   if (!throbbing_view_)
     return;
 
   // If not immediate, cycle through 2 more complete cycles.
   throbbing_view_->StartThrobbing(immediate ? 0 : 4);
   throbbing_view_ = nullptr;
 }
 
 // static
 base::string16 BookmarkBarView::CreateToolTipForURLAndTitle(
-    const views::Widget* widget,
-    const gfx::Point& screen_loc,
+    int max_width,
+    const gfx::FontList& tt_fonts,
     const GURL& url,
     const base::string16& title) {
-  const views::TooltipManager* tooltip_manager = widget->GetTooltipManager();
-  int max_width = tooltip_manager->GetMaxWidth(screen_loc);
-  const gfx::FontList tt_fonts = tooltip_manager->GetFontList();
   base::string16 result;
 
   // First the title.
   if (!title.empty()) {
     base::string16 localized_title = title;
     base::i18n::AdjustStringForLocaleDirection(&localized_title);
     result.append(gfx::ElideText(localized_title, tt_fonts, max_width,
                                  gfx::ELIDE_TAIL));
   }
 
@@ skipping 1385 matching lines @@
     return;
   apps_page_shortcut_->SetVisible(visible);
   UpdateBookmarksSeparatorVisibility();
   LayoutAndPaint();
 }
 
 void BookmarkBarView::OnShowManagedBookmarksPrefChanged() {
   if (UpdateOtherAndManagedButtonsVisibility())
     LayoutAndPaint();
 }