Revert "Add extra check for not_loaded_image_resources_ modifications while iterating"

This reverts commit 90815a3a.

Reason for revert: Real bug was identified and change is no longer necessary. crbug.com/1108676

Original change's description:
> Add extra check for not_loaded_image_resources_ modifications while iterating
>
> not_loaded_image_resources_ is being modified while iterating.
> If this CHECK doesn't catch anything, it means weak processing is triggering while iterating even though it shouldn't be.
>
> Bug: 1108676
> Change-Id: Iae00862b28fe3e324ac654c1e57834071ce5ddc9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2392021
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Commit-Queue: Keishi Hattori <keishi@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#804078}

TBR=haraken@chromium.org,keishi@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1108676
Change-Id: Ia46490f0abafafc5afac9b1971740b0afa21b10d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490967Reviewed-by: Keishi Hattori <keishi@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Keishi Hattori <keishi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819786}

third_party/blink/renderer/platform/loader/fetch/resource_fetcher.cc

@@ -1152,9 +1152,6 @@ Resource* ResourceFetcher::RequestResource(FetchParameters& params,
   LoadBlockingPolicy load_blocking_policy = LoadBlockingPolicy::kDefault;
   if (resource->GetType() == ResourceType::kImage) {
     image_resources_.insert(resource);
-#if DCHECK_IS_ON()
-    DCHECK(!not_loaded_image_resources_is_being_iterated_);
-#endif
     not_loaded_image_resources_.insert(resource);
     if (params.GetImageRequestBehavior() ==
         FetchParameters::kNonBlockingImage) {
@@ -1725,11 +1722,6 @@ bool ResourceFetcher::ShouldDeferImageLoad(const KURL& url) const {
 }
 
 void ResourceFetcher::ReloadImagesIfNotDeferred() {
-#if DCHECK_IS_ON()
-  DCHECK(!not_loaded_image_resources_is_being_iterated_);
-  base::AutoReset<bool> is_being_modified_resetter(
-      &not_loaded_image_resources_is_being_iterated_, true);
-#endif
   for (Resource* resource : not_loaded_image_resources_) {
     DCHECK_EQ(resource->GetType(), ResourceType::kImage);
     if (resource->StillNeedsLoad() && !ShouldDeferImageLoad(resource->Url()))
@@ -2077,11 +2069,6 @@ void ResourceFetcher::UpdateAllImageResourcePriorities() {
       "ResourceLoadPriorityOptimizer::updateAllImageResourcePriorities");
 
   HeapVector<Member<Resource>> to_be_removed;
-#if DCHECK_IS_ON()
-  DCHECK(!not_loaded_image_resources_is_being_iterated_);
-  base::AutoReset<bool> is_being_modified_resetter(
-      &not_loaded_image_resources_is_being_iterated_, true);
-#endif
   for (Resource* resource : not_loaded_image_resources_) {
     DCHECK_EQ(resource->GetType(), ResourceType::kImage);
     if (resource->IsLoaded()) {

third_party/blink/renderer/platform/loader/fetch/resource_fetcher.h

@@ -424,11 +424,6 @@ class PLATFORM_EXPORT ResourceFetcher
   // optimizations and might still contain images which are actually loaded.
   HeapHashSet<WeakMember<Resource>> not_loaded_image_resources_;
 
-#if DCHECK_IS_ON()
-  // TODO(keishi): Added to check for crbug.com/1108676 Remove when fixed.
-  bool not_loaded_image_resources_is_being_iterated_ = false;
-#endif
-
   HeapHashMap<PreloadKey, Member<Resource>> preloads_;
   HeapVector<Member<Resource>> matched_preloads_;
   Member<MHTMLArchive> archive_;