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..f7844879994b9c5f83ec8b67b717940ebf68a84e 100644
--- a/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
+++ b/Source/platform/image-decoders/gif/GIFImageDecoderTest.cpp
@@ -499,3 +499,31 @@ 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());
+    const size_t fullLength = fullData->size();

[Peter Kasting, 2015/01/08 06:56:18]

Nit: I'd probably omit this temp and just do the call below, but up to you.

[Alpha Left Google, 2015/01/12 22:12:49]

Done.

+
+    OwnPtr<GIFImageDecoder> decoder;
+    IntSize frameSize;
+
+    // Compute hashes when the file is truncated.
+    const size_t increment = 1;

[Peter Kasting, 2015/01/08 06:56:18]

If you're not going to use a random increment size or something here, I'd
eliminate this and just use "++i" in the loop below.

[Alpha Left Google, 2015/01/12 22:12:49]

Done.

+    for (size_t i = 1; i <= fullLength; i += increment) {
+        decoder = createDecoder();
+        RefPtr<SharedBuffer> data = SharedBuffer::create(fullData->data(), i);
+        decoder->setData(data.get(), i == fullLength);
+
+        if (decoder->isSizeAvailable() && !frameSize.width() && !frameSize.height())
+            frameSize = decoder->decodedSize();

[Peter Kasting, 2015/01/08 06:56:18]

It seems like this should just continue, since this assignment makes the rest of
the loop vacuous.

[Alpha Left Google, 2015/01/12 22:12:49]

Done.

+
+        EXPECT_EQ(frameSize.width(), decoder->decodedSize().width());
+        EXPECT_EQ(frameSize.height(), decoder->decodedSize().height());
+
+        if (frameSize.width() != decoder->decodedSize().width()
+            || frameSize.height() != decoder->decodedSize().height())
+            break;

[Peter Kasting, 2015/01/08 06:56:18]

Why not just ASSERT_EQ above and omit this conditional?

[Alpha Left Google, 2015/01/12 22:12:49]

Done.

+    }
+}