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..36689239c5596f4141d468c370aa14f858b61993 100644
--- a/third_party/WebKit/Source/core/loader/ImageLoader.cpp
+++ b/third_party/WebKit/Source/core/loader/ImageLoader.cpp
@@ -313,6 +313,11 @@ void ImageLoader::doUpdateFromElement(BypassMainWorldBehavior bypassBehavior,
     configureRequest(request, bypassBehavior, *m_element,
                      document.clientHintsPreferences());
 
+    if (updateBehavior != UpdateForcedReload && document.settings() &&
+        document.settings()->fetchImagePlaceholders()) {
+      request.setAllowImagePlaceholder();
+    }
+
     newImage = ImageResource::fetch(request, document.fetcher());
 
     if (!newImage && !pageIsBeingDismissed(&document)) {