Don't remove empty display item pairs that draw content

Source/platform/graphics/paint/FilterDisplayItem.cpp

Index: Source/platform/graphics/paint/FilterDisplayItem.cpp
diff --git a/Source/platform/graphics/paint/FilterDisplayItem.cpp b/Source/platform/graphics/paint/FilterDisplayItem.cpp
index 683b2686e8b86c868154ad9636e512a391a17e6e..293f08125fd9fdaf8e62cde6c359f2f26120796a 100644
--- a/Source/platform/graphics/paint/FilterDisplayItem.cpp
+++ b/Source/platform/graphics/paint/FilterDisplayItem.cpp
@@ -40,6 +40,12 @@ void BeginFilterDisplayItem::appendToWebDisplayItemList(WebDisplayItemList* list
     list->appendFilterItem(*m_webFilterOperations, FloatRect(m_bounds));
 }
 
+bool BeginFilterDisplayItem::drawsContent() const
+{
+    // A filter with no inputs must produce its own content.
+    return m_imageFilter->countInputs() == 0;
+}
+
 #ifndef NDEBUG
 void BeginFilterDisplayItem::dumpPropertiesAsDebugString(WTF::StringBuilder& stringBuilder) const
 {