Use LANCZOS3 resize algorithm to generate missing image reps for extension action icons.

ui/gfx/image/image_skia_operations.h

 // 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.
 
 #ifndef UI_GFX_IMAGE_SKIA_OPERATIONS_H_
 #define UI_GFX_IMAGE_SKIA_OPERATIONS_H_
 
 #include "base/gtest_prod_util.h"
 #include "skia/ext/image_operations.h"
 #include "ui/base/ui_export.h"
@@ skipping 61 matching lines @@
   static ImageSkia CreateButtonBackground(SkColor color,
                                           const gfx::ImageSkia& image,
                                           const gfx::ImageSkia& mask);
 
   // Returns an image which is a subset of |image| with bounds |subset_bounds|.
   // The |image| cannot use kA1_Config config.
   static ImageSkia ExtractSubset(const gfx::ImageSkia& image,
                                  const gfx::Rect& subset_bounds);
 
   // Creates an image by resizing |source| to given |target_dip_size|.
+  // If |source| is missing the representation for a required scale factor, the
+  // representation for the scale factor will be generated by resizing one of
+  // |source|'s existing representations' bitmap to the target pixel size.

[pkotwicz, 2012/10/17 18:42:20]

Nit: mention that we are resizing using |methd| in this case.

[tbarzic, 2012/10/17 19:00:46]

Done.

   static ImageSkia CreateResizedImage(const ImageSkia& source,
                                       skia::ImageOperations::ResizeMethod methd,
                                       const Size& target_dip_size);
 
+  // Creates an image which inherits image representations from |source|.
+  // Image representations for the scale factors not containted in |source| are
+  // generated by resizing existing representations using |resize_method|.
+  static ImageSkia SetFallbackResizeMethod(

[pkotwicz, 2012/10/17 18:42:20]

How about GetImageWithCustomResizeMethod() ?

[tbarzic, 2012/10/17 19:00:46]

yeah, sounds much better (I'll use 'Create' instead of 'Get' to be consistent
with the rest of the names in the file)..

+      const ImageSkia& source,
+      skia::ImageOperations::ResizeMethod method);
+
   // Creates an image with drop shadow defined in |shadows| for |source|.
   static ImageSkia CreateImageWithDropShadow(const ImageSkia& source,
                                              const ShadowValues& shadows);
 
  private:
   ImageSkiaOperations();  // Class for scoping only.
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_IMAGE_IMAGE_SKIA_OPERATIONS_H_