Update icon loading API implementation

chromium_src/chrome/browser/icon_loader.h

@@ -8,31 +8,30 @@
 #include <memory>
 #include <string>
 
+#include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "build/build_config.h"
 #include "content/public/browser/browser_thread.h"
 #include "ui/gfx/image/image.h"
 
-#if defined(OS_WIN)
-// On Windows, we group files by their extension, with several exceptions:
-// .dll, .exe, .ico. See IconManager.h for explanation.
-typedef std::wstring IconGroupID;
-#elif defined(OS_POSIX)
-// On POSIX, we group files by MIME type.
-typedef std::string IconGroupID;
-#endif
-
 ////////////////////////////////////////////////////////////////////////////////
 //
 // A facility to read a file containing an icon asynchronously in the IO
 // thread. Returns the icon in the form of an ImageSkia.
 //
 ////////////////////////////////////////////////////////////////////////////////
-class IconLoader : public base::RefCountedThreadSafe<IconLoader> {
+class IconLoader {
  public:
+  // An IconGroup is a class of files that all share the same icon. For all
+  // platforms but Windows, and for most files on Windows, it is the file type
+  // (e.g. all .mp3 files share an icon, all .html files share an icon). On
+  // Windows, for certain file types (.exe, .dll, etc), each file of that type
+  // is assumed to have a unique icon. In that case, each of those files is a
+  // group to itself.
+  using IconGroup = base::FilePath::StringType;
+
   enum IconSize {
     SMALL = 0,  // 16x16
     NORMAL,     // 32x32
@@ -40,42 +39,32 @@ class IconLoader : public base::RefCountedThreadSafe<IconLoader> {
     ALL,        // All sizes available
   };
 
-  class Delegate {
-   public:
-    // Invoked when an icon group has been read, but before the icon data
-    // is read. If the icon is already cached, this method should call and
-    // return the results of OnImageLoaded with the cached image.
-    virtual bool OnGroupLoaded(IconLoader* source,
-                               const IconGroupID& group) = 0;
-    // Invoked when an icon has been read. |source| is the IconLoader. If the
-    // icon has been successfully loaded, result is non-null. This method must
-    // return true if it is taking ownership of the returned image.
-    virtual bool OnImageLoaded(IconLoader* source,
-                               gfx::Image* result,
-                               const IconGroupID& group) = 0;
+  // The callback invoked when an icon has been read. The parameters are:
+  // - The icon that was loaded, or null if there was a failure to load it.
+  // - The determined group from the original requested path.
+  using IconLoadedCallback =
+      base::Callback<void(std::unique_ptr<gfx::Image>, const IconGroup&)>;
 
-   protected:
-    virtual ~Delegate() {}
-  };
+  // Creates an IconLoader, which owns itself. If the IconLoader might outlive
+  // the caller, be sure to use a weak pointer in the |callback|.
+  static IconLoader* Create(const base::FilePath& file_path,
+                            IconSize size,
+                            IconLoadedCallback callback);
 
-  IconLoader(const base::FilePath& file_path,
-             IconSize size,
-             Delegate* delegate);
-
-  // Start reading the icon on the file thread.
+  // Starts the process of reading the icon. When the reading of the icon is
+  // complete, the IconLoadedCallback callback will be fulfilled, and the
+  // IconLoader will delete itself.
   void Start();
 
  private:
-  friend class base::RefCountedThreadSafe<IconLoader>;
+  IconLoader(const base::FilePath& file_path,
+             IconSize size,
+             IconLoadedCallback callback);
 
-  virtual ~IconLoader();
+  ~IconLoader();
 
-  // Get the identifying string for the given file. The implementation
-  // is in icon_loader_[platform].cc.
-  static IconGroupID ReadGroupIDFromFilepath(const base::FilePath& path);
-
-  // Some icons (exe's on windows) can change as they're loaded.
-  static bool IsIconMutableFromFilepath(const base::FilePath& path);
+  // Given a file path, get the group for the given file.
+  static IconGroup GroupForFilepath(const base::FilePath& file_path);
 
   // The thread ReadIcon() should be called on.
   static content::BrowserThread::ID ReadIconThreadID();
@@ -84,20 +73,18 @@ class IconLoader : public base::RefCountedThreadSafe<IconLoader> {
   void OnReadGroup();
   void ReadIcon();
 
-  void NotifyDelegate();
-
   // The task runner object of the thread in which we notify the delegate.
   scoped_refptr<base::SingleThreadTaskRunner> target_task_runner_;
 
   base::FilePath file_path_;
 
-  IconGroupID group_;
+  IconGroup group_;
 
   IconSize icon_size_;
 
   std::unique_ptr<gfx::Image> image_;
 
-  Delegate* delegate_;
+  IconLoadedCallback callback_;
 
   DISALLOW_COPY_AND_ASSIGN(IconLoader);
 };