Update the nine patch layer to use UI resources

cc/resources/ui_resource_bitmap.h

 // Copyright 2013 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 CC_RESOURCES_UI_RESOURCE_BITMAP_H_
 #define CC_RESOURCES_UI_RESOURCE_BITMAP_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
+#include "third_party/skia/include/core/SkPixelRef.h"
 #include "third_party/skia/include/core/SkTypes.h"
 #include "ui/gfx/size.h"
 
+class SkBitmap;
+
 namespace cc {
 
 // Ref-counted bitmap class (can’t use SkBitmap because of ETC1).  Thread-safety
 // ensures that both main and impl threads can hold references to the bitmap and
 // that asynchronous uploads are allowed.
-class CC_EXPORT UIResourceBitmap
-    : public base::RefCountedThreadSafe<UIResourceBitmap> {
+class CC_EXPORT UIResourceBitmap {
  public:
   enum UIResourceFormat {
-    RGBA8
+    RGBA8,
+    INVALID_FORMAT
   };
 
-  // Takes ownership of “pixels”.
-  static scoped_refptr<UIResourceBitmap> Create(uint8_t* pixels,
-                                                UIResourceFormat format,
-                                                gfx::Size size);
-
   gfx::Size GetSize() const { return size_; }
   UIResourceFormat GetFormat() const { return format_; }
-  uint8_t* GetPixels() { return pixels_.get(); }
+  uint8_t* GetPixels() const;
+
+  UIResourceBitmap(SkPixelRef* pixel_ref,

[danakj, 2013/09/05 19:23:38]

Is this passing ownership with a raw pointer? If so, please don't.

[powei, 2013/09/05 20:37:35]

SkPixelRef is ref-counted, so this is not taking ownership but increasing the
ref-count.  I could mention in a comment that SkPixelRef passed in here should
already be marked immutable.  There's a DCHECK on this already.

[danakj, 2013/09/05 20:38:57]

Please use skia::RefPtr, and skia::AdoptRef() a reference as soon as you see the
raw pointer. Never store/pass raw pointers to skia ref counted things in
chromium.

[powei, 2013/09/05 21:34:08]

Done.  Thanks for letting me know.  This is much better.

+                   UIResourceFormat format,
+                   gfx::Size size);
+
+  explicit UIResourceBitmap(const SkBitmap& skbitmap);
+
+  UIResourceBitmap(const UIResourceBitmap& src);
+
+  UIResourceBitmap& operator=(const UIResourceBitmap& src);
+
+  explicit UIResourceBitmap();
+
+  ~UIResourceBitmap();
 
  private:
-  friend class base::RefCountedThreadSafe<UIResourceBitmap>;
+  void Create(SkPixelRef* pixel_ref, UIResourceFormat format, gfx::Size size);
 
-  UIResourceBitmap();
-  ~UIResourceBitmap();
-
-  scoped_ptr<uint8_t[]> pixels_;
+  SkPixelRef* pixel_ref_;

[jdduke (slow), 2013/09/05 18:39:53]

Hmm, if we're going to use an SkPixelRef backing, can we not simply go ahead and
use an SkBitmap, rather than a naked ref? Copying the SkBitmap will do the right
thing if the source is immutable, and if not we can make the copy (then set
immutable)... I'm not sure, but it might make some of the
bookkeeping/refcounting simpler.

[aelias_OOO_until_Jul13, 2013/09/05 18:42:32]

No, because we intend to support ETC1 compressed bitmaps.  These aren't
supported by SkBitmap and it would be unnecessarily hard for them to be (e.g.
the implementation of getPixel(x, y) would be complicated).

[jdduke (slow), 2013/09/05 18:51:05]

I see, though I wasn't proposing we expose the SkBitmap, rather simply use it as
the ref-counting handle.  The user would still supply an SkPixelRef, but
internally it would be contained by an SkBitmap... maybe not worth it?

[powei, 2013/09/05 20:37:35]

I'm a little worried that might cause some confusion down the road (using
SkBitmap not for its intended purpose but as a container for SkPixelRef).  That
said, please check the actual implementation to make sure that my
ref-counting/bookkeeping is correct.

[aelias_OOO_until_Jul13, 2013/09/06 04:17:37]

I think SkPixelRef is the right level of abstraction for what we're doing here. 
If you're suggesting use an SkBitmap and lie to Skia about it being RGBA8,
that's confusing and may have hidden pitfalls based on assumptions that Skia
makes about its properties.

   UIResourceFormat format_;
   gfx::Size size_;
-
-  DISALLOW_COPY_AND_ASSIGN(UIResourceBitmap);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_UI_RESOURCE_BITMAP_H_