DO NOT COMMIT: Experimental removal of encoded image data

third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * 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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 69 matching lines @@
     return wrapUnique(new DeferredImageDecoder(std::move(actualDecoder)));
 }
 
 DeferredImageDecoder::DeferredImageDecoder(std::unique_ptr<ImageDecoder> actualDecoder)
     : m_allDataReceived(false)
     , m_actualDecoder(std::move(actualDecoder))
     , m_repetitionCount(cAnimationNone)
     , m_hasColorProfile(false)
     , m_canYUVDecode(false)
     , m_hasHotSpot(false)
+    , m_isBufferCleared(false)
 {
 }
 
 DeferredImageDecoder::~DeferredImageDecoder()
 {
 }
 
 String DeferredImageDecoder::filenameExtension() const
 {
     return m_actualDecoder ? m_actualDecoder->filenameExtension() : m_filenameExtension;
@@ skipping 21 matching lines @@
     if (!m_actualDecoder || m_actualDecoder->failed())
         return nullptr;
 
     ImageFrame* frame = m_actualDecoder->frameBufferAtIndex(index);
     if (!frame || frame->getStatus() == ImageFrame::FrameEmpty)
         return nullptr;
 
     return SkImage::MakeFromBitmap(frame->bitmap());
 }
 
+bool DeferredImageDecoder::clear()
+{
+    if (!m_rwBuffer)
+        return false;
+    m_rwBuffer.reset();
+    m_isBufferCleared = true;
+    return true;
+}
+
 PassRefPtr<SharedBuffer> DeferredImageDecoder::data()
 {
     if (!m_rwBuffer)
         return nullptr;
     sk_sp<SkROBuffer> roBuffer(m_rwBuffer->newRBufferSnapshot());
     RefPtr<SharedBuffer> sharedBuffer = SharedBuffer::create();
     SkROBuffer::Iter it(roBuffer.get());
     do {
         sharedBuffer->append(static_cast<const char*>(it.data()), it.size());
     } while (it.next());
@@ skipping 17 matching lines @@
 
     if (m_frameGenerator) {
         if (!m_rwBuffer)
             m_rwBuffer = wrapUnique(new SkRWBuffer(data->size()));
 
         const char* segment = 0;
         for (size_t length = data->getSomeData(segment, m_rwBuffer->size());
             length; length = data->getSomeData(segment, m_rwBuffer->size())) {
             m_rwBuffer->append(segment, length);
         }
+        m_isBufferCleared = false;
     }
 }
 
 bool DeferredImageDecoder::isSizeAvailable()
 {
     // m_actualDecoder is 0 only if image decoding is deferred and that means
     // the image header decoded successfully and the size is available.
     return m_actualDecoder ? m_actualDecoder->isSizeAvailable() : true;
 }
 
@@ skipping 139 matching lines @@
 {
     return SkImageInfo::MakeN32(decodedSize.width(), decodedSize.height(), knownToBeOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 }
 
 sk_sp<SkImage> DeferredImageDecoder::createFrameImageAtIndex(size_t index, bool knownToBeOpaque)
 {
     const SkISize& decodedSize = m_frameGenerator->getFullSize();
     ASSERT(decodedSize.width() > 0);
     ASSERT(decodedSize.height() > 0);
 
+    DCHECK(!m_isBufferCleared);
     sk_sp<SkROBuffer> roBuffer(m_rwBuffer->newRBufferSnapshot());
     RefPtr<SegmentReader> segmentReader = SegmentReader::createFromSkROBuffer(std::move(roBuffer));
     DecodingImageGenerator* generator = new DecodingImageGenerator(m_frameGenerator, imageInfoFrom(decodedSize, knownToBeOpaque), segmentReader.release(), m_allDataReceived, index, m_frameData[index].m_uniqueID);
     sk_sp<SkImage> image = SkImage::MakeFromGenerator(generator); // SkImage takes ownership of the generator.
     if (!image)
         return nullptr;
 
     // We can consider decoded bitmap constant and reuse uniqueID only after all
     // data is received.  We reuse it also for multiframe images when image data
     // is partially received but the frame data is fully received.
@@ skipping 17 matching lines @@
 }
 
 } // namespace blink
 
 namespace WTF {
 template<> struct VectorTraits<blink::DeferredFrameData> : public SimpleClassVectorTraits<blink::DeferredFrameData> {
     STATIC_ONLY(VectorTraits);
     static const bool canInitializeWithMemset = false; // Not all DeferredFrameData members initialize to 0.
 };
 }