Checking if frame is complete and access duration doesn't need a decode

Source/core/platform/image-decoders/ImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008-2009 Torch Mobile, Inc.
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 275 matching lines @@
 
         virtual int repetitionCount() const { return cAnimationNone; }
 
         // Decodes as much of the requested frame as possible, and returns an
         // ImageDecoder-owned pointer.
         virtual ImageFrame* frameBufferAtIndex(size_t) = 0;
 
         // Make the best effort guess to check if the requested frame has alpha channel.
         virtual bool frameHasAlphaAtIndex(size_t) const;
 
+        // Whether or not the frame is completely decoded or fully received.
+        // This method is used by animated images only.

[Peter Kasting, 2013/04/23 21:43:20]

I'm not terribly comfortable with this comment.  It may be currently true that
we only wind up calling this during animation (I'm not actually sure), but I
think the API of this class should support calling this for any image, meaning
we should provide a real implementation in the .cpp file.

Doing so should be easy and will greatly simplify the frameHasAlphaAtIndex()
implementation which basically implements the "frame complete?" check inline as
most of the function.

[Alpha Left Google, 2013/04/25 23:02:44]

I'm pretty sure this API is used only for animated images.

I agree with you that this API shouldn't be restricted to animated images. I'll
leave this as a TODO as simplifying frameHasAlphaAtIndex() and having a default
implementation for non-animated images is not a goal for this CL.

[Peter Kasting, 2013/04/25 23:22:32]

But you're adding the function in this CL, and the implementation that works for
both image types is like 2 lines long.  Why not do it now?  It's trivial.

+        virtual bool frameIsCompleteAtIndex(size_t) const { return false; }
+
+        // Duration for displaying a frame in seconds. This method is used by animated images only.
+        virtual float frameDurationAtIndex(size_t) const { return 0; }
+
         // Number of bytes in the decoded frame requested. Return 0 if not yet decoded.
         virtual unsigned frameBytesAtIndex(size_t) const;
 
         void setIgnoreGammaAndColorProfile(bool flag) { m_ignoreGammaAndColorProfile = flag; }
         bool ignoresGammaAndColorProfile() const { return m_ignoreGammaAndColorProfile; }
 
         ImageOrientation orientation() const { return m_orientation; }
 
         enum { iccColorProfileHeaderLength = 128 };
 
@@ skipping 115 matching lines @@
         IntSize m_size;
         bool m_sizeAvailable;
         int m_maxNumPixels;
         bool m_isAllDataReceived;
         bool m_failed;
     };
 
 } // namespace WebCore
 
 #endif