Do not consolidate data in BMPImageDecoder

Source/platform/image-decoders/FastSharedBufferReader.cpp

 /*
  * Copyright (C) 2015 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 23 matching lines @@
 namespace blink {
 
 FastSharedBufferReader::FastSharedBufferReader(PassRefPtr<SharedBuffer> data)
     : m_data(data)
     , m_segment(0)
     , m_segmentLength(0)
     , m_dataPosition(0)
 {
 }
 
+void FastSharedBufferReader::setData(PassRefPtr<SharedBuffer> data)
+{
+    if (data == m_data)
+        return;
+    m_data = data;
+    m_segment = 0;
+    m_segmentLength = 0;
+    m_dataPosition = 0;
+}
+
 const char* FastSharedBufferReader::getConsecutiveData(size_t dataPosition, size_t length, char* buffer)
 {
     RELEASE_ASSERT(dataPosition + length <= m_data->size());
 
     // Use the cached segment if it can serve the request.
     if (dataPosition >= m_dataPosition && dataPosition + length <= m_dataPosition + m_segmentLength)
         return m_segment + dataPosition - m_dataPosition;
 
     // Return a pointer into |m_data| if the request doesn't span segments.
     getSomeDataInternal(dataPosition);
@@ skipping 21 matching lines @@
 }
 
 void FastSharedBufferReader::getSomeDataInternal(unsigned dataPosition)
 {
     m_dataPosition = dataPosition;
     m_segmentLength = m_data->getSomeData(m_segment, dataPosition);
     ASSERT(m_segmentLength);
 }
 
 } // namespace blink