Record Data Savings for Client-Side LoFi

third_party/WebKit/Source/core/loader/resource/ImageResource.cpp

Index: third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
diff --git a/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp b/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
index 0537ade286012b5626f6cd80dc25801b246ad731..c5c664d4ceb9389c92184cfe591a4619b93c23a9 100644
--- a/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
+++ b/third_party/WebKit/Source/core/loader/resource/ImageResource.cpp
@@ -494,7 +494,20 @@ void ImageResource::ReloadIfLoFiOrPlaceholderImage(
 
   SetCachePolicyBypassingCache();
 
-  SetPreviewsStateNoTransform();
+  // The reloaded image should not use any previews transformations.
+  WebURLRequest::PreviewsState previews_state_for_reload =
+      WebURLRequest::kPreviewsNoTransform;
+
+  if (policy == kReloadIfNeeded && (GetResourceRequest().GetPreviewsState() &
+                                    WebURLRequest::kClientLoFiOn)) {
+    // If the image attempted to use Client LoFi, but encountered a decoding
+    // error and is being automatically reloaded, then also set the appropriate
+    // PreviewsState bit for that. This allows the embedder to count the
+    // bandwidth used for this reload against the data savings of the initial
+    // response.
+    previews_state_for_reload |= WebURLRequest::kClientLoFiAutoReload;
+  }
+  SetPreviewsState(previews_state_for_reload);
 
   if (placeholder_option_ != PlaceholderOption::kDoNotReloadPlaceholder)
     ClearRangeRequestHeader();