Remove opaque alpha channel special case

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.cpp

 /*
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Library General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
  *
  *  This library is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 273 matching lines @@
 
   if (frame_buffer_cache_[index].GetStatus() != ImageFrame::kFrameComplete)
     return false;
 
   if (purge_aggressively_)
     ClearCacheExceptFrame(index);
 
   return true;
 }
 
-void ImageDecoder::CorrectAlphaWhenFrameBufferSawNoAlpha(size_t index) {
-  DCHECK(index < frame_buffer_cache_.size());
-  ImageFrame& buffer = frame_buffer_cache_[index];
-
-  // When this frame spans the entire image rect we can SetHasAlpha to false,
-  // since there are logically no transparent pixels outside of the frame rect.
-  if (buffer.OriginalFrameRect().Contains(IntRect(IntPoint(), Size()))) {
-    buffer.SetHasAlpha(false);
-    buffer.SetRequiredPreviousFrameIndex(kNotFound);
-  } else if (buffer.RequiredPreviousFrameIndex() != kNotFound) {
-    // When the frame rect does not span the entire image rect, and it does
-    // *not* have a required previous frame, the pixels outside of the frame
-    // rect will be fully transparent, so we shoudn't SetHasAlpha to false.
-    //
-    // It is a tricky case when the frame does have a required previous frame.
-    // The frame does not have alpha only if everywhere outside its rect
-    // doesn't have alpha.  To know whether this is true, we check the start
-    // state of the frame -- if it doesn't have alpha, we're safe.
-    //
-    // We first check that the required previous frame does not have
-    // DisposeOverWritePrevious as its disposal method - this should never
-    // happen, since the required frame should in that case be the required
-    // frame of this frame's required frame.
-    //
-    // If |prev_buffer| is DisposeNotSpecified or DisposeKeep, |buffer| has no
-    // alpha if |prev_buffer| had no alpha. Since InitFrameBuffer() already
-    // copied the alpha state, there's nothing to do here.
-    //
-    // The only remaining case is a DisposeOverwriteBgcolor frame.  If
-    // it had no alpha, and its rect is contained in the current frame's
-    // rect, we know the current frame has no alpha.
-    //
-    // For DisposeNotSpecified, DisposeKeep and DisposeOverwriteBgcolor there
-    // is one situation that is not taken into account - when |prev_buffer|
-    // *does* have alpha, but only in the frame rect of |buffer|, we can still
-    // say that this frame has no alpha. However, to determine this, we
-    // potentially need to analyze all image pixels of |prev_buffer|, which is
-    // too computationally expensive.
-    const ImageFrame* prev_buffer =
-        &frame_buffer_cache_[buffer.RequiredPreviousFrameIndex()];
-    DCHECK(prev_buffer->GetDisposalMethod() !=
-           ImageFrame::kDisposeOverwritePrevious);
-
-    if ((prev_buffer->GetDisposalMethod() ==
-         ImageFrame::kDisposeOverwriteBgcolor) &&
-        !prev_buffer->HasAlpha() &&
-        buffer.OriginalFrameRect().Contains(prev_buffer->OriginalFrameRect()))
-      buffer.SetHasAlpha(false);
-  }
-}
-
 bool ImageDecoder::InitFrameBuffer(size_t frame_index) {
   DCHECK(frame_index < frame_buffer_cache_.size());
 
   ImageFrame* const buffer = &frame_buffer_cache_[frame_index];
 
   // If the frame is already initialized, return true.
   if (buffer->GetStatus() != ImageFrame::kFrameEmpty)
     return true;
 
   size_t required_previous_frame_index = buffer->RequiredPreviousFrameIndex();
@@ skipping 222 matching lines @@
     }
 
     // For color spaces without an identifiable gamut, just fall through to
     // sRGB.
   }
 
   return SkColorSpace::MakeSRGB();
 }
 
 }  // namespace blink