Load 2x resources on demand

chrome/browser/themes/browser_theme_pack.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/themes/browser_theme_pack.h"
 
 #include <limits>
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 418 matching lines @@
   pack->BuildSourceImagesArray(file_paths);
 
   if (!pack->LoadRawBitmapsTo(file_paths, &pack->images_on_ui_thread_))
     return NULL;
 
   pack->CopyImagesTo(pack->images_on_ui_thread_, &pack->images_on_file_thread_);
 
   pack->CreateImages(&pack->images_on_ui_thread_);
   pack->CreateImages(&pack->images_on_file_thread_);
 
+  // Make sure the images_on_file_thread_ has bitmaps for supported
+  // scale factors before passing to FILE thread.
+  for (ImageCache::iterator it = pack->images_on_file_thread_.begin();
+       it != pack->images_on_file_thread_.end(); ++it) {
+    gfx::ImageSkia* image_skia =
+        const_cast<gfx::ImageSkia*>(it->second->ToImageSkia());
+    image_skia->EnsureRepsForSupportedScaleFactors();
+    image_skia->DeleteSource();
+  }

[pkotwicz, 2012/08/23 16:58:48]

Why don't you make images_on_ui_thread_ have images for all supported scale
factors and then do a copy to images_on_file_thread_?
Also you don't need the code below: pack->GenerateImageReps() anymore.

[oshima, 2012/08/23 17:16:50]

Because images in UI thread only needs scales that are in use.
It'd be waste of memory to load them all. That's why I was asking if we can
release images_on_file_thread_ after it's written.
Ah, you're right. Thank you for the catch! Done.

+
   // For M22, as it is not possible to easily determine which scale factors are
   // in use, assume that the 1x scale factor is in use.
   std::vector<ui::ScaleFactor> scale_factors_in_use;
   scale_factors_in_use.push_back(ui::SCALE_FACTOR_100P);
   pack->GenerateImageReps(scale_factors_in_use);
 
   // The BrowserThemePack is now in a consistent state.
   return pack;
 }
 
@@ skipping 775 matching lines @@
     ui::ScaleFactor scale_factor) const {
   if (prs_id < 0)
     return -1;
 
   for (size_t i = 0; i < scale_factors_.size(); ++i) {
     if (scale_factors_[i] == scale_factor)
       return static_cast<int>(kPersistingImagesLength * i) + prs_id;
   }
   return -1;
 }