Fix caching bug in JPEGImageDecoder

Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp

Index: Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
diff --git a/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp b/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
index 59ae3c81f2557edeef572f0a271593353c66cf7b..514ebcf24035046ee73f3c5be5a4bf4faa782ca8 100644
--- a/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
+++ b/Source/platform/image-decoders/jpeg/JPEGImageDecoderTest.cpp
@@ -240,4 +240,48 @@ TEST(JPEGImageDecoderTest, byteByByte)
     testByteByByteDecode(&createDecoder, "/LayoutTests/fast/images/resources/red-at-12-oclock-with-color-profile.jpg", 1u, cAnimationNone);
 }
 
+static unsigned createDecodingBaseline(SharedBuffer* data)
+{
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(data, true);
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    return hashBitmap(frame->bitmap());
+}
+
+// This test verifies that calling SharedBuffer::mergeSegmentsIntoBuffer() does
+// not break JPEG decoding at a critical point: in between a call to decode the
+// size (when JPEGImageDecoder stops while it may still have input data to
+// read) and a call to do a full decode.
+TEST(JPEGImageDecoderTest, mergeBuffer)
+{
+    const char* jpegFile = "/LayoutTests/fast/images/resources/lenna.jpg";
+    RefPtr<SharedBuffer> data = readFile(jpegFile);
+    ASSERT_TRUE(data);
+
+    const unsigned hash = createDecodingBaseline(data.get());
+
+    // In order to do any verification, this test needs to move the data owned
+    // by the SharedBuffer. A way to guarantee that is to create a new one, and
+    // then append a string of characters greater than kSegmentSize. This
+    // results in writing the data into a segment, skipping the internal
+    // contiguous buffer.
+    RefPtr<SharedBuffer> segmentedData = SharedBuffer::create();
+    segmentedData->append(data->data(), data->size());
+
+    OwnPtr<ImageDecoder> decoder = createDecoder();
+    decoder->setData(segmentedData.get(), true);
+
+    ASSERT_TRUE(decoder->isSizeAvailable());
+
+    // This will call SharedBuffer::mergeSegmentsIntoBuffer, copying all
+    // segments into the contiguous buffer. If JPEGImageDecoder was pointing to
+    // data in a segment, its pointer would no longer be valid.
+    segmentedData->data();
+
+    ImageFrame* frame = decoder->frameBufferAtIndex(0);
+    ASSERT_FALSE(decoder->failed());
+    EXPECT_EQ(frame->status(), ImageFrame::FrameComplete);
+    EXPECT_EQ(hashBitmap(frame->bitmap()), hash);
+}
+
 } // namespace blink