Re-land: Blink image-decoders: (lazy) deferred image decoding support for ICO

third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp

Index: third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp b/third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp
index e50b37c361ee927d03183f39e764da215a702aef..00d19d7eba0776767bf69ae1cb21bd02216c6ecb 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/ico/ICOImageDecoder.cpp
@@ -85,6 +85,14 @@ bool ICOImageDecoder::setSize(unsigned width, unsigned height)
     return m_frameSize.isEmpty() ? ImageDecoder::setSize(width, height) : ((IntSize(width, height) == m_frameSize) || setFailed());
 }
 
+bool ICOImageDecoder::frameIsCompleteAtIndex(size_t index) const
+{
+    if (index >= m_dirEntries.size())
+        return false;
+    const IconDirectoryEntry& dirEntry = m_dirEntries[index];
+    return (dirEntry.m_imageOffset + dirEntry.m_byteSize) <= m_data->size();
+}
+
 bool ICOImageDecoder::setFailed()
 {
     m_bmpReaders.clear();
@@ -122,6 +130,19 @@ bool ICOImageDecoder::compareEntries(const IconDirectoryEntry& a, const IconDire
 size_t ICOImageDecoder::decodeFrameCount()
 {
     decodeSize();
+
+    // If decodeSize() fails, return the existing number of frames.  This way
+    // if we get halfway through the image before decoding fails, we won't
+    // suddenly start reporting that the image has zero frames.
+    if (failed())
+        return m_frameBufferCache.size();
+
+    // Length of sequence of completely received frames.
+    for (size_t i = 0; i < m_dirEntries.size(); ++i) {
+        const IconDirectoryEntry& dirEntry = m_dirEntries[i];
+        if ((dirEntry.m_imageOffset + dirEntry.m_byteSize) > m_data->size())
+            return i;
+    }
     return m_dirEntries.size();
 }
 
@@ -175,13 +196,12 @@ bool ICOImageDecoder::decodeAtIndex(size_t index)
 
     if (imageType == BMP) {
         if (!m_bmpReaders[index]) {
-            // We need to have already sized m_frameBufferCache before this, and
-            // we must not resize it again later (see caution in frameCount()).
-            ASSERT(m_frameBufferCache.size() == m_dirEntries.size());
             m_bmpReaders[index] = adoptPtr(new BMPImageReader(this, dirEntry.m_imageOffset, 0, true));
             m_bmpReaders[index]->setData(m_data.get());
-            m_bmpReaders[index]->setBuffer(&m_frameBufferCache[index]);
         }
+        // Update the pointer to the buffer as it could change after
+        // m_frameBufferCache.resize().
+        m_bmpReaders[index]->setBuffer(&m_frameBufferCache[index]);
         m_frameSize = dirEntry.m_size;
         bool result = m_bmpReaders[index]->decodeBMP(false);
         m_frameSize = IntSize();
@@ -280,6 +300,7 @@ ICOImageDecoder::IconDirectoryEntry ICOImageDecoder::readDirectoryEntry()
         entry.m_bitCount = readUint16(6);
         entry.m_hotSpot = IntPoint();
     }
+    entry.m_byteSize = readUint32(8);
     entry.m_imageOffset = readUint32(12);
 
     // Some icons don't have a bit depth, only a color count.  Convert the