Fix dead-lock issue attempting to decode

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

Index: third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp b/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
index 160ecd439c10e0ffc56a7cbc3f685abdacd469c0..bfe12625d9b40fd24892e7c195c3c23689a6a498 100644
--- a/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DecodingImageGenerator.cpp
@@ -54,7 +54,19 @@ SkData* DecodingImageGenerator::onRefEncodedData(GrContext* ctx)
 {
     TRACE_EVENT0("blink", "DecodingImageGenerator::refEncodedData");
 
-    return m_allDataReceived ? m_data->getAsSkData().leakRef() : nullptr;
+    // The GPU only wants the data if it has all been received, since the GPU
+    // only wants a complete texture. getAsSkData() may require copying, so
+    // skip it and just return nullptr to avoid a slowdown. (See
+    // crbug.com/568016 for details about such a slowdown.)
+    // TODO (scroggo): Stop relying on the internal knowledge of how Skia uses
+    // this. skbug.com/5485
+    if (ctx && !m_allDataReceived)
+        return nullptr;
+
+    // Other clients are serializers, which want the data even if it requires
+    // copying, and even if the data is incomplete. (Otherwise they would
+    // potentially need to decode the partial image in order to re-encode it.)
+    return m_data->getAsSkData().leakRef();
 }
 
 bool DecodingImageGenerator::onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes, SkPMColor table[], int* tableCount)