Web Animations CSS: Fix crash when transitioning background or mask properties

Source/core/rendering/style/FillLayer.cpp

Index: Source/core/rendering/style/FillLayer.cpp
diff --git a/Source/core/rendering/style/FillLayer.cpp b/Source/core/rendering/style/FillLayer.cpp
index fc784c84092c30e7e77a810e09b3de9dfc540e28..c4b48bf0a2f3bfd83f58db04a9139453cd702f09 100644
--- a/Source/core/rendering/style/FillLayer.cpp
+++ b/Source/core/rendering/style/FillLayer.cpp
@@ -40,7 +40,7 @@ struct SameSizeAsFillLayer {
 
 COMPILE_ASSERT(sizeof(FillLayer) == sizeof(SameSizeAsFillLayer), FillLayer_should_stay_small);
 
-FillLayer::FillLayer(EFillLayerType type)
+FillLayer::FillLayer(EFillLayerType type, bool useInitialValues)
     : m_next(0)
     , m_image(FillLayer::initialFillImage(type))
     , m_xPosition(FillLayer::initialFillXPosition(type))
@@ -52,24 +52,24 @@ FillLayer::FillLayer(EFillLayerType type)
     , m_repeatX(FillLayer::initialFillRepeatX(type))
     , m_repeatY(FillLayer::initialFillRepeatY(type))
     , m_composite(FillLayer::initialFillComposite(type))
-    , m_sizeType(SizeNone) // SizeNone indicates size is unset.
+    , m_sizeType(useInitialValues ? FillLayer::initialFillSizeType(type) : SizeNone)
     , m_blendMode(FillLayer::initialFillBlendMode(type))
     , m_maskSourceType(FillLayer::initialFillMaskSourceType(type))
     , m_backgroundXOrigin(LeftEdge)
     , m_backgroundYOrigin(TopEdge)
-    , m_imageSet(false)
-    , m_attachmentSet(false)
-    , m_clipSet(false)
-    , m_originSet(false)
-    , m_repeatXSet(false)
-    , m_repeatYSet(false)
-    , m_xPosSet(false)
-    , m_yPosSet(false)
-    , m_backgroundXOriginSet(false)
-    , m_backgroundYOriginSet(false)
-    , m_compositeSet(type == MaskFillLayer)
-    , m_blendModeSet(false)
-    , m_maskSourceTypeSet(false)
+    , m_imageSet(useInitialValues)
+    , m_attachmentSet(useInitialValues)
+    , m_clipSet(useInitialValues)
+    , m_originSet(useInitialValues)
+    , m_repeatXSet(useInitialValues)
+    , m_repeatYSet(useInitialValues)
+    , m_xPosSet(useInitialValues)
+    , m_yPosSet(useInitialValues)
+    , m_backgroundXOriginSet(useInitialValues)
+    , m_backgroundYOriginSet(useInitialValues)
+    , m_compositeSet(useInitialValues || type == MaskFillLayer)
+    , m_blendModeSet(useInitialValues)
+    , m_maskSourceTypeSet(useInitialValues)
     , m_type(type)
 {
 }