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

Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp

Index: Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
diff --git a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
index 8186836744e475eca8dfb52e889356b9924b5817..d785aec0341c6f5f782e4ffe3b97e4b74b001224 100644
--- a/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
+++ b/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
@@ -127,6 +127,18 @@ ImageFrame* GIFImageDecoder::frameBufferAtIndex(size_t index)
     return &frame;
 }
 
+bool GIFImageDecoder::frameIsCompleteAtIndex(size_t index) const
+{
+    return m_reader && (index < m_reader->imagesCount()) && m_reader->frameContext(index)->isComplete();
+}
+
+float GIFImageDecoder::frameDurationAtIndex(size_t index) const
+{
+    return (m_reader && (index < m_reader->imagesCount()) &&
+        m_reader->frameContext(index)->isHeaderDefined()) ?
+        m_reader->frameContext(index)->delayTime : 0;
+}
+
 bool GIFImageDecoder::setFailed()
 {
     m_reader.clear();
@@ -185,7 +197,7 @@ void GIFImageDecoder::clearFrameBufferCache(size_t clearBeforeFrame)
 
 bool GIFImageDecoder::haveDecodedRow(unsigned frameIndex, const Vector<unsigned char>& rowBuffer, size_t width, size_t rowNumber, unsigned repeatCount, bool writeTransparentPixels)
 {
-    const GIFFrameContext* frameContext = m_reader->frameContext();
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     // The pixel data and coordinates supplied to us are relative to the frame's
     // origin within the entire image size, i.e.
     // (frameContext->xOffset, frameContext->yOffset). There is no guarantee
@@ -297,8 +309,6 @@ void GIFImageDecoder::gifComplete()
     // Cache the repetition count, which is now as authoritative as it's ever
     // going to be.
     repetitionCount();
-
-    m_reader.clear();
 }
 
 void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query)
@@ -335,16 +345,16 @@ void GIFImageDecoder::decode(unsigned haltAtFrame, GIFQuery query)
         return;
     }
 
-    // It is also a fatal error if all data is received but we failed to decode
-    // all frames completely.
-    if (isAllDataReceived() && haltAtFrame >= m_frameBufferCache.size() && m_reader)
+    // It is also a fatal error if all data is received and we have decoded all
+    // frames available but the file is truncated.
+    if (haltAtFrame >= m_frameBufferCache.size() && isAllDataReceived() && m_reader && !m_reader->parseCompleted())
         setFailed();
 }
 
 bool GIFImageDecoder::initFrameBuffer(unsigned frameIndex)
 {
     // Initialize the frame rect in our buffer.
-    const GIFFrameContext* frameContext = m_reader->frameContext();
+    const GIFFrameContext* frameContext = m_reader->frameContext(frameIndex);
     IntRect frameRect(frameContext->xOffset, frameContext->yOffset, frameContext->width, frameContext->height);
 
     // Make sure the frameRect doesn't extend outside the buffer.