Always select best favicon bitmap

components/favicon/core/favicon_handler.h

Index: components/favicon/core/favicon_handler.h
diff --git a/components/favicon/core/favicon_handler.h b/components/favicon/core/favicon_handler.h
index f3d9d4b662c5d9c6f034cacffc7f5a8cfd67d9db..45db6d59b0754c189762cc89047bb97d26e898f8 100644
--- a/components/favicon/core/favicon_handler.h
+++ b/components/favicon/core/favicon_handler.h
@@ -68,14 +68,63 @@ class FaviconService;
 // favicon.
 //
 // When the renderer downloads favicons, it considers the entire list of
-// favicon candidates, if |download_largest_favicon_| is true, the largest
-// favicon will be used, otherwise the one that best matches the preferred size
-// is chosen (or the first one if there is no preferred  size). Once the
-// matching favicon has been determined, SetFavicon is called which updates
-// the page's favicon and notifies the database to save the favicon.
+// favicon candidates. Among those, the one that matches |target_spec_|
+// is chosen first. Once the matching favicon has been determined, SetFavicon
+// is called which updates the page's favicon and notifies the database to save
+// the favicon.
 
 class FaviconHandler {
  public:
+  class TargetSpec {
+   public:
+    static TargetSpec ForLargest();
+    static TargetSpec For16x16Dips();
+
+    TargetSpec(const TargetSpec&);
+    ~TargetSpec();
+
+    // Returns the target sizes to be fetched, sorted in ascending order.
+    // FaviconHandler will ensure a bitmap for each pixel sizes
+    // either by searching among candidates for an exact match, or by resampling
+    // the closest match.
+    std::vector<int> GetPixelSizes() const;
+
+    // Returns the maximum value instead of all.
+    int GetMaxPixelSize() const;
+
+    // Returns whether the spec is requiring the best-matching bitmap only.
+    bool WantsBestBitmapOnly() const;
+
+    // Compares two sizes in pixels, i.e. whether |size1| is a better match than
+    // |size2| for |pixel_size|.
+    bool IsBetterMatch(const gfx::Size& size1, const gfx::Size& size2) const;
+
+    // Checks if |bitmap_results| contains all bitmaps required by this
+    // specification.
+    bool HasCompleteResult(
+        const std::vector<favicon_base::FaviconRawBitmapResult>& bitmap_results)
+        const;
+
+    gfx::ImageSkia CreateImageSkia(
+        const std::vector<SkBitmap>& bitmaps,
+        const std::vector<gfx::Size>& original_bitmap_sizes) const;
+
+    gfx::Image CreateImageFromCache(
+        const std::vector<favicon_base::FaviconRawBitmapResult>& bitmap_results)
+        const;
+
+   private:
+    TargetSpec();
+
+    // Map representing the target sizes to be fetched and their corresponding
+    // scale factors.
+    std::map<int, float> pixel_sizes_;
+
+    // If true, FaviconHandler will resample candidates whenever needed to
+    // ensure that bitmaps for all |pixel_sizes| are produced.
+    bool ensure_exact_size_;
+  };
+
   class Delegate {
    public:
     // Mimics WebContents::ImageDownloadCallback.
@@ -162,12 +211,10 @@ class FaviconHandler {
 
     FaviconCandidate(const GURL& image_url,
                      const gfx::Image& image,
-                     float score,
                      favicon_base::IconType icon_type);
 
     GURL image_url;
     gfx::Image image;
-    float score;
     favicon_base::IconType icon_type;
   };
 
@@ -208,10 +255,10 @@ class FaviconHandler {
 
   bool ShouldSaveFavicon();
 
-  // Updates |favicon_candidate_| and returns true if it is an exact match.
+  // Updates |favicon_candidate_| and returns true if no more candidates should
+  // be processed (e.g. an exact match was found).
   bool UpdateFaviconCandidate(const GURL& image_url,
                               const gfx::Image& image,
-                              float score,
                               favicon_base::IconType icon_type);
 
   // Sets the image data for the favicon.
@@ -238,12 +285,6 @@ class FaviconHandler {
                : nullptr;
   }
 
-  // Returns the preferred size of the image. 0 means no preference (any size
-  // will do).
-  int preferred_icon_size() const {
-    return download_largest_icon_ ? 0 : gfx::kFaviconSize;
-  }
-
   // Used for FaviconService requests.
   base::CancelableTaskTracker cancelable_task_tracker_;
 
@@ -274,8 +315,8 @@ class FaviconHandler {
   // The combination of the supported icon types.
   const int icon_types_;
 
-  // Whether the largest icon should be downloaded.
-  const bool download_largest_icon_;
+  // Desired icon size.
+  const TargetSpec target_spec_;
 
   // The prioritized favicon candidates from the page back from the renderer.
   std::vector<favicon::FaviconURL> image_urls_;