Add Blink support for showing image placeholders using range requests.

third_party/WebKit/Source/core/loader/ImageLoader.cpp

Index: third_party/WebKit/Source/core/loader/ImageLoader.cpp
diff --git a/third_party/WebKit/Source/core/loader/ImageLoader.cpp b/third_party/WebKit/Source/core/loader/ImageLoader.cpp
index 296a26d1d3ed5e4277e875d80a80ea782b5c9407..0b4c8d75e7bee06524b1e355e3fff8949bbee1d9 100644
--- a/third_party/WebKit/Source/core/loader/ImageLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/ImageLoader.cpp
@@ -313,6 +313,12 @@ void ImageLoader::doUpdateFromElement(BypassMainWorldBehavior bypassBehavior,
     configureRequest(request, bypassBehavior, *m_element,
                      document.clientHintsPreferences());
 
+    request.setPlaceholderImageRequestType(
+        updateBehavior != UpdateForcedReload && document.settings() &&
+                document.settings()->fetchImagePlaceholders()
+            ? FetchRequest::AllowPlaceholder
+            : FetchRequest::DisallowPlaceholder);
+
     newImage = ImageResource::fetch(request, document.fetcher());
 
     if (!newImage && !pageIsBeingDismissed(&document)) {