GIF decoding to Index8, unit tests and misusing unit test as benchmark

third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp

Index: third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
index 1411c494248a4a21170f245dc5e8aaa5899035ae..e4a18a6741ef49be0291dc4a4e47e624a1e9bfb2 100644
--- a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoder.cpp
@@ -228,6 +228,8 @@ void DeferredImageDecoder::activateLazyDecoding()
 
     const bool isSingleFrame = m_actualDecoder->repetitionCount() == cAnimationNone || (m_allDataReceived && m_actualDecoder->frameCount() == 1u);
     m_frameGenerator = ImageFrameGenerator::create(SkISize::Make(m_actualDecoder->decodedSize().width(), m_actualDecoder->decodedSize().height()), m_data, m_allDataReceived, !isSingleFrame);
+    // GIF images support Index8 decoding: other decoders do not.
+    m_frameGenerator->setDecoderCanDecodeToIndex8(m_filenameExtension == "gif");
 }
 
 void DeferredImageDecoder::prepareLazyDecodedFrames()
@@ -268,7 +270,7 @@ void DeferredImageDecoder::prepareLazyDecodedFrames()
     }
 }
 
-inline SkImageInfo imageInfoFrom(const SkISize& decodedSize, bool knownToBeOpaque)
+static inline SkImageInfo imageInfoFrom(const SkISize& decodedSize, bool knownToBeOpaque)
 {
     return SkImageInfo::MakeN32(decodedSize.width(), decodedSize.height(), knownToBeOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
 }
@@ -279,8 +281,13 @@ PassRefPtr<SkImage> DeferredImageDecoder::createFrameImageAtIndex(size_t index,
     ASSERT(decodedSize.width() > 0);
     ASSERT(decodedSize.height() > 0);
 
-    DecodingImageGenerator* generator = new DecodingImageGenerator(m_frameGenerator, imageInfoFrom(decodedSize, knownToBeOpaque), index);
-    RefPtr<SkImage> image = adoptRef(SkImage::NewFromGenerator(generator)); // SkImage takes ownership of the generator.
+    const SkImageInfo info = m_frameGenerator->canDecodeTo(index, kIndex_8_SkColorType)
+        ? SkImageInfo::Make(decodedSize.width(), decodedSize.height(), kIndex_8_SkColorType,
+            knownToBeOpaque ? kOpaque_SkAlphaType : kPremul_SkAlphaType)
+        : imageInfoFrom(decodedSize, knownToBeOpaque);
+
+    DecodingImageGenerator* generator = new DecodingImageGenerator(m_frameGenerator, info, index);
+    RefPtr<SkImage> image = adoptRef(SkImage::NewFromGenerator(generator));
     if (!image)
         return nullptr;