Fix handling of broken GIFs with weird frame sizes

Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp

Index: Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
diff --git a/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp b/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
index db39a29bfc4c3c35fdb767c8285ea3a882eae7cd..ae2f2c89cf33364af0d52aadb95de116eb8806e6 100644
--- a/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
+++ b/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
@@ -499,3 +499,27 @@ TEST(GIFImageDecoderTest, invalidDisposalMethod)
     // Disposal method 5 is ignored.
     EXPECT_EQ(ImageFrame::DisposeNotSpecified, decoder->frameBufferAtIndex(1)->disposalMethod());
 }
+
+TEST(GIFImageDecoderTest, firstFrameHasGreaterSizeThanScreenSize)
+{
+    RefPtr<SharedBuffer> fullData = readFile("/Source/platform/image-decoders/testing/first-frame-has-greater-size-than-screen-size.gif");
+    ASSERT_TRUE(fullData.get());
+
+    OwnPtr<GIFImageDecoder> decoder;
+    IntSize frameSize;
+
+    // Compute hashes when the file is truncated.
+    for (size_t i = 1; i <= fullData->size(); ++i) {
+        decoder = createDecoder();
+        RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(), i);
+        decoder->setData(data.get(), i == fullData->size());
+
+        if (decoder->isSizeAvailable() && !frameSize.width() && !frameSize.height()) {
+            frameSize = decoder->decodedSize();
+            continue;
+        }
+
+        ASSERT_EQ(frameSize.width(), decoder->decodedSize().width());
+        ASSERT_EQ(frameSize.height(), decoder->decodedSize().height());
+    }
+}