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();

[sky, 2012/08/23 16:32:32]

This is too error prone. I think we should make it so ImageSkia CHECKs your on
the UI thread always. If some one needs to use it off the UI thread they should
copy out the bitmaps.

[oshima, 2012/08/23 16:57:31]

Yes it's error prone and that's why I added NonThreadSafe and
DCHECK(CalledOnValidThread())
in ImageSkia. That's how this has been detected.

Unfortunately, we can't check if it's UI thread (In fact, I tried it first)
because this is ui:: component and can't depend on content. Also, this is used
in renderer process where there is no UI thread.
images_on_file_thread_ IS copy of image_on_ui_thread_. This is to make sure
that images_on_file_thread_ has all bitmaps so that FILE thread do not have to
load them. Alternative way is to detach these ImageSkia from UI thread so that
FILE thread can load them. This is also safe because they're copy and won't be
used
by UI thread after this.

+       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();
+  }
+
   // 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;
 }