Remove external BitmapImage lazy decoding tracking

Source/platform/graphics/ImageSource.cpp

Index: Source/platform/graphics/ImageSource.cpp
diff --git a/Source/platform/graphics/ImageSource.cpp b/Source/platform/graphics/ImageSource.cpp
index c441f8acefc2645a54abb061221822337469846e..2fbb2f15ee6b009d41118f71cf7f92b71b1ad1c3 100644
--- a/Source/platform/graphics/ImageSource.cpp
+++ b/Source/platform/graphics/ImageSource.cpp
@@ -143,11 +143,6 @@ bool ImageSource::frameIsCompleteAtIndex(size_t index) const
     return m_decoder && m_decoder->frameIsCompleteAtIndex(index);
 }
 
-bool ImageSource::frameIsLazyDecodedAtIndex(size_t index) const
-{
-    return m_decoder && m_decoder->frameIsCachedAndLazyDecodedAtIndex(index);
-}
-
 size_t ImageSource::frameBytesAtIndex(size_t index) const
 {
     return m_decoder ? m_decoder->frameBytesAtIndex(index) : 0;