WIP: Implement APNG

third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp

Index: third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp
diff --git a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp
index 5281c1ba065c9005ab9e27924de31e316852d74c..e59ed8a0b8fc41f4192b25ff0d447c40e491cce3 100644
--- a/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp
+++ b/third_party/WebKit/Source/platform/image-decoders/png/PNGImageDecoderTest.cpp
@@ -5,9 +5,31 @@
 #include "platform/image-decoders/png/PNGImageDecoder.h"
 
 #include "platform/image-decoders/ImageDecoderTestHelpers.h"
+#include "png.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include <memory>
 
+// /LayoutTests/images/resources/png-animated-idat-part-of-animation.png
+// is modified in multiple tests to simulate erroneous PNGs. As a reference,
+// the table below shows how the file is structured.
+//
+// Offset | 8     33    95    133   172   210   241   279   314   352   422
+// -------------------------------------------------------------------------
+// Chunk  | IHDR  acTL  fcTL  IDAT  fcTL  fdAT  fcTL  fdAT  fcTL  fdAT  IEND
+//
+// In between the acTL and fcTL there are two other chunks, PLTE and tRNS, but
+// those are not specifically used in this test suite. The same holds for a
+// tEXT chunk in between the last fdAT and IEND.
+//
+// In the current behavior of PNG image decoders, the 4 frames are detected when
+// respectively 141, 249, 322 and 430 bytes are received. The first frame should
+// be detected when the IDAT has been received, and non-first frames when the
+// next fcTL or IEND chunk has been received. Note that all offsets are +8,
+// because a chunk is identified by byte 4-7.
+
+// @TODO(joostouwerling) extend test image set with other image encodings, such
+//                       as first frame fcTL and multiple chunks per frame.
+
 namespace blink {
 
 namespace {
@@ -37,14 +59,161 @@ void testSize(const char* pngFile, IntSize expectedSize) {
   EXPECT_EQ(expectedSize, decoder->size());
 }
 
+// Test whether querying for the size of the image works if we present the
+// data byte by byte.
+void testSizeByteByByte(const char* pngFile,
+                        size_t bytesNeededToDecodeSize,
+                        IntSize expectedSize) {
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+  ASSERT_LT(bytesNeededToDecodeSize, data->size());
+
+  for (size_t length = 1; length <= bytesNeededToDecodeSize; length++) {
+    RefPtr<SharedBuffer> tempData = SharedBuffer::create(data->data(), length);
+    decoder->setData(tempData.get(), false);
+
+    if (length < bytesNeededToDecodeSize) {
+      EXPECT_FALSE(decoder->isSizeAvailable());
+      EXPECT_TRUE(decoder->size().isEmpty());
+      EXPECT_FALSE(decoder->failed());
+    } else {
+      EXPECT_TRUE(decoder->isSizeAvailable());
+      EXPECT_EQ(expectedSize, decoder->size());
+    }
+  }
+  EXPECT_FALSE(decoder->failed());
+}
+
+void writeUint32(uint32_t val, png_byte* data) {
+  data[0] = val >> 24;
+  data[1] = val >> 16;
+  data[2] = val >> 8;
+  data[3] = val;
+}
+
 void testRepetitionCount(const char* pngFile, int expectedRepetitionCount) {
   auto decoder = createDecoderWithPngData(pngFile);
-  // Decoding the frame count sets the repetition count as well.
+  // Decode frame count should see the number of repetitions as well.
   decoder->frameCount();
   EXPECT_FALSE(decoder->failed());
   EXPECT_EQ(expectedRepetitionCount, decoder->repetitionCount());
 }
 
+struct PublicFrameInfo {
+  size_t duration;
+  IntRect frameRect;
+  ImageFrame::AlphaBlendSource alphaBlend;
+  ImageFrame::DisposalMethod disposalMethod;
+};
+
+// This is the frame data for the following PNG image:
+// /LayoutTests/images/resources/png-animated-idat-part-of-animation.png
+static PublicFrameInfo pngAnimatedFrameInfo[] = {
+    {500,
+     {IntPoint(0, 0), IntSize(5, 5)},
+     ImageFrame::BlendAtopBgcolor,
+     ImageFrame::DisposeKeep},
+    {900,
+     {IntPoint(1, 1), IntSize(3, 1)},
+     ImageFrame::BlendAtopBgcolor,
+     ImageFrame::DisposeOverwriteBgcolor},
+    {2000,
+     {IntPoint(1, 2), IntSize(3, 2)},
+     ImageFrame::BlendAtopPreviousFrame,
+     ImageFrame::DisposeKeep},
+    {1500,
+     {IntPoint(1, 2), IntSize(3, 1)},
+     ImageFrame::BlendAtopBgcolor,
+     ImageFrame::DisposeKeep},
+};
+
+void compareFrameWithExpectation(const PublicFrameInfo& expected,
+                                 const ImageFrame* frame) {
+  EXPECT_EQ(expected.duration, frame->duration());
+  EXPECT_EQ(expected.frameRect, frame->originalFrameRect());
+  EXPECT_EQ(expected.disposalMethod, frame->getDisposalMethod());
+  EXPECT_EQ(expected.alphaBlend, frame->getAlphaBlendSource());
+}
+
+// This function removes |length| bytes at |offset|, and then calls frameCount.
+// It assumes the missing bytes should result in a failed decode because the
+// parser jumps |length| bytes too far in the next chunk.
+void testMissingDataBreaksDecoding(const char* pngFile,
+                                   size_t offset,
+                                   size_t length) {
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+
+  RefPtr<SharedBuffer> invalidData = SharedBuffer::create(data->data(), offset);
+  invalidData->append(data->data() + offset + length,
+                      data->size() - offset - length);
+  ASSERT_EQ(data->size() - length, invalidData->size());
+
+  decoder->setData(invalidData, true);
+  decoder->frameCount();
+  EXPECT_TRUE(decoder->failed());
+}
+
+// Decoding up to the indicated fcTL offset and then provide an fcTL with
+// the wrong chunk size (20 instead of 26). It should break the decoder.
+void testInvalidFctlSize(const char* pngFile,
+                         size_t offsetFctl,
+                         size_t expectedFrameCountBeforeFail,
+                         bool expectedDecoderFailure) {
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+
+  auto decoder = createDecoder();
+  RefPtr<SharedBuffer> invalidData =
+      SharedBuffer::create(data->data(), offsetFctl);
+
+  // Test if this gives the correct frame count, before the fcTL is parsed.
+  decoder->setData(invalidData, false);
+  EXPECT_EQ(expectedFrameCountBeforeFail, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+
+  // Append the wrong size to the data stream
+  png_byte sizeChunk[4];
+  writeUint32(20, sizeChunk);
+  invalidData->append(reinterpret_cast<char*>(sizeChunk), 4u);
+
+  // Skip the size in the original data, but provide the rest of the fcTL,
+  // which is 4B of tag, 26B of data and 4B of CRC, totalling 34B.
+  invalidData->append(data->data() + offsetFctl + 4, 34u);
+
+  decoder->setData(invalidData, false);
+  decoder->frameCount();
+  EXPECT_EQ(expectedDecoderFailure, decoder->failed());
+}
+
+void testDifferentActlFrameCountIsIgnored(const char* pngFile,
+                                          size_t offsetActl,
+                                          size_t injectedFrameCount,
+                                          size_t expectedFrameCount) {
+  // First make sure that this tests makes sense.
+  ASSERT_NE(injectedFrameCount, expectedFrameCount);
+
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+
+  RefPtr<SharedBuffer> diffActlData =
+      SharedBuffer::create(data->data(), offsetActl + 8);
+  // Write the injectedFrameCount to the stream
+  png_byte sizeChunk[4];
+  writeUint32(injectedFrameCount, sizeChunk);
+  diffActlData->append(reinterpret_cast<char*>(sizeChunk), 4u);
+  // Append the rest of the data. The first |offsetActl + 12| bytes that are
+  // already in diffActlData should not be appended again.
+  diffActlData->append(data->data() + offsetActl + 12,
+                       data->size() - offsetActl - 12);
+
+  decoder->setData(diffActlData, true);
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+}
+
 // Verify that the decoder can successfully decode the first frame when
 // initially only half of the frame data is received, resulting in a partially
 // decoded image, and then the rest of the image data is received. Verify that
@@ -60,7 +229,7 @@ void testProgressiveDecodingContinuesAfterFullData(const char* pngFile,
 
   auto decoderUpfront = createDecoder();
   decoderUpfront->setData(fullData.get(), true);
-  EXPECT_GE(1u, decoderUpfront->frameCount());
+  EXPECT_GE(decoderUpfront->frameCount(), 1u);
   const ImageFrame* const frameUpfront = decoderUpfront->frameBufferAtIndex(0);
   ASSERT_EQ(ImageFrame::FrameComplete, frameUpfront->getStatus());
   const unsigned hashUpfront = hashBitmap(frameUpfront->bitmap());
@@ -114,16 +283,507 @@ void testFailureDuringDecode(const char* file,
 
   EXPECT_EQ(expectedFrameCountBefore, decoder->frameCount());
 
-  const ImageFrame* const frame = decoder->frameBufferAtIndex(frameIndex);
-  EXPECT_EQ(expectFailure, decoder->failed());
+  decoder->frameBufferAtIndex(frameIndex);
+  ASSERT_EQ(expectFailure, decoder->failed());
   if (!expectFailure) {
     EXPECT_EQ(expectedFrameCountAfter, decoder->frameCount());
-    EXPECT_EQ(ImageFrame::FrameEmpty, frame->getStatus());
+    EXPECT_EQ(nullptr, decoder->frameBufferAtIndex(frameIndex));
   }
 }
 
 }  // Anonymous namespace
 
+// Animated PNG Tests
+
+TEST(AnimatedPNGTests, sizeTest) {
+  testSize(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      IntSize(5, 5));
+  testSize(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-not-part-of-animation.png",
+      IntSize(227, 35));
+}
+
+TEST(AnimatedPNGTests, repetitionCountTest) {
+  testRepetitionCount(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      7u);
+  // This is an "animated" image with only one frame, that is, the IDAT is
+  // ignored and there is one fdAT frame. so it should be considered
+  // non-animated.
+  testRepetitionCount(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-not-part-of-animation.png",
+      cAnimationNone);
+}
+
+// Test if the decoded metdata corresponds to the defined expectations
+TEST(AnimatedPNGTests, MetaDataTest) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  constexpr size_t expectedFrameCount = 4;
+
+  auto decoder = createDecoderWithPngData(pngFile);
+  ASSERT_EQ(expectedFrameCount, decoder->frameCount());
+  for (size_t i = 0; i < expectedFrameCount; i++) {
+    compareFrameWithExpectation(pngAnimatedFrameInfo[i],
+                                decoder->frameBufferAtIndex(i));
+  }
+}
+
+TEST(AnimatedPNGTests, ByteByByteSizeAvailable) {
+  testSizeByteByByte(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      141u, IntSize(5, 5));
+  testSizeByteByByte(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-not-part-of-animation.png",
+      79u, IntSize(227, 35));
+}
+
+// Test whether the frame metadata decoding also works when we provide the data
+// byte by byte. This should cover the case when the client does not provide
+// all data at once. At given offsets, we expect frames to become available.
+// This test checks whether that is the case, and if so, if the frame data is
+// equal to what we expected.
+TEST(AnimatedPNGTests, ByteByByteMetaData) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  constexpr size_t expectedFrameCount = 4;
+
+  // These are the byte offsets where each frame should have been parsed.
+  // It boils down to the offset of the first fcTL / IEND after the last
+  // frame data chunk, plus 8 bytes for recognition. The exception on this is
+  // the first frame, which is reported when its first framedata is seen.
+  size_t frameOffsets[expectedFrameCount] = {141, 249, 322, 430};
+
+  auto decoder = createDecoder();
+  auto data = readFile(pngFile);
+  ASSERT_FALSE(data->isEmpty());
+  size_t framesParsed = 0;
+
+  for (size_t length = 1; length <= frameOffsets[expectedFrameCount - 1];
+       length++) {
+    RefPtr<SharedBuffer> tempData = SharedBuffer::create(data->data(), length);
+    decoder->setData(tempData.get(), false);
+    EXPECT_FALSE(decoder->failed());
+    if (length < frameOffsets[framesParsed]) {
+      EXPECT_EQ(framesParsed, decoder->frameCount());
+    } else {
+      ASSERT_EQ(framesParsed + 1, decoder->frameCount());
+      compareFrameWithExpectation(pngAnimatedFrameInfo[framesParsed],
+                                  decoder->frameBufferAtIndex(framesParsed));
+      framesParsed++;
+    }
+  }
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+TEST(AnimatedPNGTests, TestRandomFrameDecode) {
+  testRandomFrameDecode(&createDecoder,
+                        "/LayoutTests/images/resources/"
+                        "png-animated-idat-part-of-animation.png",
+                        2u);
+}
+
+TEST(AnimatedPNGTests, TestDecodeAfterReallocation) {
+  testDecodeAfterReallocatingData(&createDecoder,
+                                  "/LayoutTests/images/resources/"
+                                  "png-animated-idat-part-of-animation.png");
+}
+
+TEST(AnimatedPNGTests, ProgressiveDecode) {
+  testProgressiveDecoding(&createDecoder,
+                          "/LayoutTests/images/resources/"
+                          "png-animated-idat-part-of-animation.png",
+                          13u);
+}
+
+TEST(AnimatedPNGTests, ParseAndDecodeByteByByte) {
+  testByteByByteDecode(&createDecoder,
+                       "/LayoutTests/images/resources/"
+                       "png-animated-idat-part-of-animation.png",
+                       4u, 7u);
+}
+
+TEST(AnimatedPNGTests, FailureDuringParsing) {
+  // Test the first fcTL in the stream. Because no frame data has been set at
+  // this point, the expected frame count is zero. 95 bytes is just before the
+  // first fcTL chunk, at which the first frame is detected. The decoder should
+  // be in the failed state since no frames were parsed before this error.
+  testInvalidFctlSize(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      95u, 0u, true);
+
+  // Test for the third fcTL in the stream. This should be tested as well,
+  // since the first fcTL is parsed in PNGImageReader::parseSize() whereas
+  // later fcTLs are parsed in PNGImageReader::parse() as part of framecount.
+  // The expected frame count before the fcTL chunk is 1u, since the second
+  // frame is registered when the third fcTL (or IEND) is seen.
+  //
+  // This should *not* set the decoder to the failed state since the first
+  // frame was succesfully parsed, and we still want to show that frame.
+  testInvalidFctlSize(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      241u, 1u, false);
+}
+
+TEST(AnimatedPNGTests, FailureDuringParsingDueToMissingFctlData) {
+  // The fcTL chunk starts at 95u, add 10u to get to the content data, and
+  // remove 5 bytes of data. This sets the decoder to the failed state since
+  // no frames were parsed yet.
+  testMissingDataBreaksDecoding(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      105u, 5u);
+}
+
+TEST(AnimatedPNGTests, MissingActlResultsInNonAnimated) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+
+  // Remove the acTL chunk from the stream.
+  const size_t offsetActl = 33;
+  RefPtr<SharedBuffer> noActlData =
+      SharedBuffer::create(data->data(), offsetActl);
+  noActlData->append(data->data() + offsetActl + 20,
+                     data->size() - offsetActl - 20);
+
+  decoder->setData(noActlData, true);
+  EXPECT_EQ(1u, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+// Test if the indicated frame count by the acTL is ignored if the actual
+// number of frames is different. Test for higher and lower indicated number.
+TEST(AnimatedPNGTests, differentActlFrameCountIsIgnored) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  testDifferentActlFrameCountIsIgnored(pngFile, 33u, 2u, 4u);
+  testDifferentActlFrameCountIsIgnored(pngFile, 33u, 8u, 4u);
+}
+
+// Originally, the third frame has an offset of (1,2) and a size of (3,2). By
+// changing the offset to (0,0) and the size to (4,4), a frame with not enough
+// data is simulated. The expected result is that the decoder will only receive
+// 1 row of data, since the data contains 6 pixels and each row is 4 pixels.
+//
+// When the decoder receives not enough data for a frame, the expected behavior
+// is that nothing changes: the decoder should not be invalidated, and the
+// frame should be considered successfully decoded. The reason for this is that
+// the error could either be an invalid frame size, or an invalid data chunk.
+// For now, the decoder does not take any action if not enough data is
+// provided, as described in PNGImageDecoder::complete().
+TEST(AnimatedPNGTests, VerifyIncompleteFrameDataDoesNotInvalidateDecoder) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+
+  // Change the size and the offset of the frame, as described above. The size
+  // is stored in byte 12-19 of the fcTL chunk, and the offset in byte 20-27.
+  const size_t offsetThirdFctl = 241 + 12;
+  RefPtr<SharedBuffer> modifiedData =
+      SharedBuffer::create(data->data(), offsetThirdFctl);
+  png_byte rectChunk[16];
+  writeUint32(4, rectChunk);
+  writeUint32(4, rectChunk + 4);
+  writeUint32(0, rectChunk + 8);
+  writeUint32(0, rectChunk + 12);
+  modifiedData->append(
+      const_cast<const char*>(reinterpret_cast<char*>(rectChunk)), 16u);
+  modifiedData->append(data->data() + offsetThirdFctl + 16,
+                       data->size() - offsetThirdFctl - 16);
+
+  decoder->setData(modifiedData, true);
+
+  // Verify that parsing the image results in the expected meta data.
+  IntSize expectedSize(5, 5);
+  const size_t expectedFrameCount = 4;
+  IntRect expectedFrameRect(IntPoint(0, 0), IntSize(4, 4));
+  EXPECT_TRUE(decoder->isSizeAvailable());
+  EXPECT_EQ(expectedSize, decoder->size());
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+
+  // Try to decode frame 3. This should not fail the decoder, and the frame
+  // should be FrameComplete.
+  const ImageFrame* const buffer = decoder->frameBufferAtIndex(2);
+  EXPECT_EQ(expectedFrameRect, buffer->originalFrameRect());
+  EXPECT_FALSE(decoder->failed());
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_EQ(ImageFrame::FrameComplete, buffer->getStatus());
+}
+
+// Originally, the third frame has an offset of (1,2) and a size of (3,2). By
+// changing the offset to (4,4), the frame rect will extend the image size of
+// 5x5. Verify that the frame is correctly clipped to a size of (1,1) without
+// any decoding errors. Since this is the third frame, a decoding failure would
+// result in the frame count being adjusted to 2, and the decoder would not be
+// invalidated. Therefore, it is verified that after decoding frame 3 the
+// decoder is still in a valid state and the frame count is still 4.
+TEST(AnimatedPNGTests, VerifyFrameExtendsImageSizeClipsCorrectly) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  auto data = readFile(pngFile);
+  auto decoder = createDecoder();
+  ASSERT_FALSE(data->isEmpty());
+
+  // The offset of the frame rect is located 20 bytes into the fcTL chunk, after
+  // the length, tag, sequence number, width and height fields (all 4B).
+  const size_t offsetThirdFctl = 241 + 20;
+  RefPtr<SharedBuffer> modifiedData =
+      SharedBuffer::create(data->data(), offsetThirdFctl);
+  png_byte offsetChunk[8];
+  writeUint32(4, offsetChunk);
+  writeUint32(4, offsetChunk + 4);
+  modifiedData->append(
+      const_cast<const char*>(reinterpret_cast<char*>(offsetChunk)), 8u);
+  modifiedData->append(data->data() + offsetThirdFctl + 8,
+                       data->size() - offsetThirdFctl - 8);
+
+  decoder->setData(modifiedData, true);
+
+  // Verify that parsing the image results in the expected meta data.
+  IntSize expectedSize(5, 5);
+  const size_t expectedFrameCount = 4;
+  IntRect expectedFrameRect(IntPoint(4, 4), IntSize(1, 1));
+  EXPECT_TRUE(decoder->isSizeAvailable());
+  EXPECT_EQ(expectedSize, decoder->size());
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+
+  // Try to decode frame 3. This should not fail the decoder, and the frame
+  // should be FrameComplete.
+  const ImageFrame* const buffer = decoder->frameBufferAtIndex(2);
+  EXPECT_EQ(expectedFrameRect, buffer->originalFrameRect());
+  EXPECT_FALSE(decoder->failed());
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_EQ(ImageFrame::FrameComplete, buffer->getStatus());
+}
+
+TEST(AnimatedPNGTests, ProgressiveDecodingContinuesAfterFullData) {
+  // 160u is a randomly chosen offset in the IDAT chunk of the first frame.
+  testProgressiveDecodingContinuesAfterFullData(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      160u);
+}
+
+TEST(AnimatedPNGTests, RandomDecodeAfterClearFrameBufferCache) {
+  testRandomDecodeAfterClearFrameBufferCache(
+      &createDecoder,
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      2u);
+}
+
+TEST(AnimatedPNGTests, VerifyAlphaBlending) {
+  testAlphaBlending(&createDecoder,
+                    "/LayoutTests/images/resources/"
+                    "png-animated-idat-part-of-animation.png");
+}
+
+// This tests if the frame count gets set correctly when parsing frameCount
+// fails in one of the parsing queries.
+//
+// First, enough data is provided such that two frames should be registered.
+// The decoder should at this point not be in the failed status.
+//
+// Then, we provide the rest of the data except for the last IEND chunk, but
+// tell the decoder that this is all the data we have.  The frame count should
+// be three, since one extra frame should be discovered. The fourth frame
+// should *not* be registered since the reader should not be able to determine
+// where the frame ends. The decoder should *not* be in the failed state since
+// there are three frames which can be shown.
+TEST(AnimatedPNGTests, FailureMissingIendChunk) {
+  RefPtr<SharedBuffer> fullData = readFile(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png");
+  ASSERT_FALSE(fullData->isEmpty());
+  auto decoder = createDecoder();
+
+  const size_t offsetTwoFrames = 249;
+  const size_t expectedFramesAfter249Bytes = 2;
+  RefPtr<SharedBuffer> tempData =
+      SharedBuffer::create(fullData->data(), offsetTwoFrames);
+  decoder->setData(tempData.get(), false);
+  EXPECT_EQ(expectedFramesAfter249Bytes, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+
+  // Provide the rest of the data except for the last IEND chunk.
+  const size_t expectedFramesAfterAllExpect12Bytes = 3;
+  tempData = SharedBuffer::create(fullData->data(), fullData->size() - 12);
+  decoder->setData(tempData.get(), true);
+  EXPECT_EQ(expectedFramesAfterAllExpect12Bytes, decoder->frameCount());
+  EXPECT_FALSE(decoder->failed());
+}
+
+TEST(AnimatedPNGTests, VerifyFrameCountChangesOnDecodingFailure) {
+  testFailureDuringDecode(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      279u,   // idat offset for frame index 2
+      2u,     // try to decode frame index 2
+      false,  // expect the decoder to *not* be invalidated after the failure
+      4u,     // expected frame count before failure
+      2u);    // expected frame count after failure
+
+  testFailureDuringDecode(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png",
+      133u,  // idat offset for frame index 0
+      0u,    // try to decode frame index 0
+      true,  // expect the decoder to be invalidated after the failure
+      4u);   // expected frame count before failure
+}
+
+// Verify that a malformatted PNG, where the IEND appears before any frame data
+// (IDAT), invalidates the decoder.
+TEST(AnimatedPNGTests, VerifyIENDBeforeIDATInvalidatesDecoder) {
+  RefPtr<SharedBuffer> fullData = readFile(
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png");
+  ASSERT_FALSE(fullData->isEmpty());
+  auto decoder = createDecoder();
+
+  const size_t offsetIDAT = 133;
+  RefPtr<SharedBuffer> data =
+      SharedBuffer::create(fullData->data(), offsetIDAT);
+  data->append(fullData->data() + fullData->size() - 12u, 12u);
+  data->append(fullData->data() + offsetIDAT, fullData->size() - offsetIDAT);
+  decoder->setData(data.get(), true);
+
+  const size_t expectedFrameCount = 0u;
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  EXPECT_TRUE(decoder->failed());
+}
+
+// For animated images, frameIsCompleteAtIndex(i) should return true if the
+// i-th frame is fully received. The frames don't need to be successfully
+// decoded.
+TEST(AnimatedPNGTests, VerifyFrameCompleteBehavior) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  RefPtr<SharedBuffer> fullData = readFile(pngFile);
+  ASSERT_FALSE(fullData->isEmpty());
+  auto decoder = createDecoder();
+
+  // When not all data for the first frame has been received,
+  // frameIsCompleteAtIndex(0) should return false.
+  const size_t offsetMidwayFirstFrame = 160;
+  RefPtr<SharedBuffer> data =
+      SharedBuffer::create(fullData->data(), offsetMidwayFirstFrame);
+  decoder->setData(data.get(), false);
+  EXPECT_EQ(1u, decoder->frameCount());
+  ASSERT_FALSE(decoder->failed());
+  EXPECT_FALSE(decoder->frameIsCompleteAtIndex(0));
+
+  // When all image data is received, every frame should be complete.
+  const size_t expectedFrameCount = 4;
+  decoder->setData(fullData.get(), true);
+  EXPECT_EQ(expectedFrameCount, decoder->frameCount());
+  for (size_t index = 0; index < expectedFrameCount; index++)
+    EXPECT_TRUE(decoder->frameIsCompleteAtIndex(index));
+}
+
+// Verify that erroneous values for the disposal method and alpha blending
+// are parsed into the expected default values, respectively DisposeNotSpecified
+// and BlendAtopBgcolor.
+TEST(AnimatedPNGTests, VerifyInvalidDisposalAndBlendingDefaultCorrectly) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-idat-part-of-animation.png";
+  RefPtr<SharedBuffer> fullData = readFile(pngFile);
+  ASSERT_FALSE(fullData->isEmpty());
+  auto decoder = createDecoder();
+
+  // The disposal byte in the frame control chunk is the 24th byte, alpha
+  // blending the 25th. |offsetDisposalOp| is 241 bytes to get to the third
+  // fctl chunk, 8 bytes to skip the length and tag bytes, and 24 bytes to get
+  // to the disposal op.
+  //
+  // Write random values to the disposal and alpha blending byte, and append
+  // the rest of the buffer.
+  const size_t offsetDisposalOp = 241 + 8 + 24;
+  RefPtr<SharedBuffer> data =
+      SharedBuffer::create(fullData->data(), offsetDisposalOp);
+  png_byte disposalAndBlending[2];
+  disposalAndBlending[0] = 7;
+  disposalAndBlending[1] = 9;
+  data->append(reinterpret_cast<char*>(disposalAndBlending), 2u);
+  data->append(fullData->data() + offsetDisposalOp + 2u,
+               fullData->size() - offsetDisposalOp - 2u);
+
+  decoder->setData(data.get(), true);
+  decoder->frameCount();
+  ASSERT_FALSE(decoder->failed());
+  EXPECT_EQ(ImageFrame::DisposalMethod::DisposeNotSpecified,
+            decoder->frameBufferAtIndex(2)->getDisposalMethod());
+  EXPECT_EQ(ImageFrame::AlphaBlendSource::BlendAtopBgcolor,
+            decoder->frameBufferAtIndex(2)->getAlphaBlendSource());
+}
+
+// This test verifies that the following situation does not invalidate the
+// decoder:
+// - Frame 0 is decoded progressively, but there's not enough data to fully
+//   decode it.
+// - The rest of the image data is received.
+// - Frame X, with X > 0, and X does not depend on frame 0, is decoded.
+// - Frame 0 is decoded.
+// This is a tricky case since the decoder resets the png struct for each frame,
+// and this test verifies that it does not break the decoding of frame 0, even
+// though it already started in the first call.
+TEST(AnimatedPNGTests, VerifySuccessfulFirstFrameDecodeAfterLaterFrame) {
+  const char* pngFile =
+      "/LayoutTests/images/resources/"
+      "png-animated-three-independent-frames.png";
+  auto decoder = createDecoder();
+  auto fullData = readFile(pngFile);
+  ASSERT_FALSE(fullData->isEmpty());
+
+  // 160u is a randomly chosen offset in the IDAT chunk of the first frame.
+  const size_t middleFirstFrame = 160u;
+  RefPtr<SharedBuffer> data =
+      SharedBuffer::create(fullData->data(), middleFirstFrame);
+  decoder->setData(data.get(), false);
+
+  ASSERT_EQ(1u, decoder->frameCount());
+  ASSERT_EQ(ImageFrame::FramePartial,
+            decoder->frameBufferAtIndex(0)->getStatus());
+
+  decoder->setData(fullData.get(), true);
+  ASSERT_EQ(3u, decoder->frameCount());
+  ASSERT_EQ(ImageFrame::FrameComplete,
+            decoder->frameBufferAtIndex(1)->getStatus());
+  // The point is that this call does not decode frame 0, which it won't do if
+  // it does not have it as its required previous frame.
+  ASSERT_EQ(kNotFound,
+            decoder->frameBufferAtIndex(1)->requiredPreviousFrameIndex());
+
+  EXPECT_EQ(ImageFrame::FrameComplete,
+            decoder->frameBufferAtIndex(0)->getStatus());
+  EXPECT_FALSE(decoder->failed());
+}
+
 // Static PNG tests
 
 TEST(StaticPNGTests, repetitionCountTest) {
@@ -144,6 +804,11 @@ TEST(StaticPNGTests, MetaDataTest) {
   EXPECT_EQ(expectedDuration, decoder->frameDurationAtIndex(0));
 }
 
+TEST(StaticPNGTests, InvalidIHDRChunk) {
+  testMissingDataBreaksDecoding("/LayoutTests/images/resources/png-simple.png",
+                                20u, 2u);
+}
+
 TEST(StaticPNGTests, ProgressiveDecoding) {
   testProgressiveDecoding(&createDecoder,
                           "/LayoutTests/images/resources/png-simple.png", 11u);