Remove external BitmapImage lazy decoding tracking

Source/platform/graphics/DeferredImageDecoder.cpp

Index: Source/platform/graphics/DeferredImageDecoder.cpp
diff --git a/Source/platform/graphics/DeferredImageDecoder.cpp b/Source/platform/graphics/DeferredImageDecoder.cpp
index 6d4538bcbe4aa73567378a9269f3aef646ca8bde..a9621b5a1058f9cd5e2404cb48dfd82615ab593d 100644
--- a/Source/platform/graphics/DeferredImageDecoder.cpp
+++ b/Source/platform/graphics/DeferredImageDecoder.cpp
@@ -177,13 +177,6 @@ bool DeferredImageDecoder::frameIsCompleteAtIndex(size_t index) const
     return false;
 }
 
-bool DeferredImageDecoder::frameIsCachedAndLazyDecodedAtIndex(size_t index) const
-{
-    // All frames cached in m_frameData are lazy-decoded.
-    ASSERT(index >= m_frameData.size() || m_frameData[index].m_haveMetadata);
-    return index < m_frameData.size();
-}
-
 float DeferredImageDecoder::frameDurationAtIndex(size_t index) const
 {
     if (m_actualDecoder)