Remove SourceGraphic reference from SkiaImageFilterBuilder

Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp

Index: Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp
diff --git a/Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp b/Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp
index 56b8d0a5d762af508a5571ffb48cde45ba21c793..c42328956ce39f405ed219d245ba03ef4ff99d0f 100644
--- a/Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp
+++ b/Source/platform/graphics/filters/SkiaImageFilterBuilder.cpp
@@ -38,15 +38,8 @@
 
 namespace blink {
 
-SkiaImageFilterBuilder::SkiaImageFilterBuilder()
-    : m_context(nullptr)
-    , m_sourceGraphic(nullptr)
-{
-}
-
 SkiaImageFilterBuilder::SkiaImageFilterBuilder(GraphicsContext* context)
     : m_context(context)
-    , m_sourceGraphic(nullptr)
 {
 }