Do not cache the tab background if a tab background was autogenerated by a theme

chrome/browser/ui/views/tabs/tab.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/tabs/tab.h"
 
 #include <limits>
 
 #include "base/command_line.h"
 #include "base/debug/alias.h"
@@ skipping 1136 matching lines @@
   if (animation->current_part_index() == 2) {
     uint8 alpha = animation->CurrentValueBetween(255, 0);
     canvas->DrawImageInt(hover_image, 0, 0, alpha);
   } else {
     canvas->DrawImageInt(hover_image, 0, 0);
   }
 }
 
 void Tab::PaintInactiveTabBackground(gfx::Canvas* canvas) {
   int tab_id;
+  int tab_base_id;
   views::Widget* widget = GetWidget();
   if (widget && widget->GetTopLevelWidget()->ShouldUseNativeFrame()) {
     tab_id = IDR_THEME_TAB_BACKGROUND_V;
+    tab_base_id = 0;

[sky, 2013/02/11 21:21:55]

Is 0 known to be ignored? I think I would rather have the if below not ask if
tab_base_id == 0. Also, wouldn't a better name for tab_base_id be frame_id?

   } else if (data().incognito) {
     tab_id = IDR_THEME_TAB_BACKGROUND_INCOGNITO;
+    tab_base_id = IDR_THEME_FRAME_INCOGNITO;
 #if defined(OS_WIN)
   } else if (win8::IsSingleWindowMetroMode()) {
     tab_id = IDR_THEME_TAB_BACKGROUND_V;
+    tab_base_id = 0;
 #endif
   } else {
     tab_id = IDR_THEME_TAB_BACKGROUND;
+    tab_base_id = IDR_THEME_FRAME;
   }
   // Explicitly map the id so we cache correctly.
   const chrome::HostDesktopType host_desktop_type = GetHostDesktopType(this);
   tab_id = chrome::MapThemeImage(host_desktop_type, tab_id);
 
-  const bool can_cache = !GetThemeProvider()->HasCustomImage(tab_id) &&
+  // Do not cache the tab background if the theme provides a custom tab
+  // background or if a tab background was autogenerated by the theme
+  // machinery.
+  ui::ThemeProvider* theme_provider = GetThemeProvider();
+  const bool can_cache = !theme_provider->HasCustomImage(tab_id) &&
+      !theme_provider->HasCustomImage(tab_base_id) &&
       !hover_controller_.ShouldDraw();
 
   if (can_cache) {
     gfx::ImageSkia cached_image(
         GetCachedImage(tab_id, size(), canvas->scale_factor()));
     if (cached_image.width() == 0) {
       gfx::Canvas tmp_canvas(size(), canvas->scale_factor(), false);
       PaintInactiveTabBackgroundUsingResourceId(&tmp_canvas, tab_id);
       cached_image = gfx::ImageSkia(tmp_canvas.ExtractImageRep());
       SetCachedImage(tab_id, canvas->scale_factor(), cached_image);
@@ skipping 458 matching lines @@
                          const gfx::ImageSkia& image) {
   DCHECK_NE(scale_factor, ui::SCALE_FACTOR_NONE);
   ImageCacheEntry entry;
   entry.resource_id = resource_id;
   entry.scale_factor = scale_factor;
   entry.image = image;
   image_cache_->push_front(entry);
   if (image_cache_->size() > kMaxImageCacheSize)
     image_cache_->pop_back();
 }