Make RendererSiderResourceLoader work well with ResourceLoadScheduler

Make IsThrottable return false when it's throttled by WebFrameScheduler.

Bug: 785770
Change-Id: Idb075c759a10636b406505287b3a1139db54678b
Reviewed-on: https://chromium-review.googlesource.com/799539
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520817}

third_party/WebKit/Source/platform/loader/fetch/ResourceLoadScheduler.cpp

@@ -243,16 +243,25 @@ void ResourceLoadScheduler::OnNetworkQuiet() {
 
 bool ResourceLoadScheduler::IsThrottablePriority(
     ResourceLoadPriority priority) const {
-  if (Platform::Current()->IsRendererSideResourceSchedulerEnabled()) {
-    if (priority >= ResourceLoadPriority::kMedium)
-      return false;
+  if (!Platform::Current()->IsRendererSideResourceSchedulerEnabled())
+    return true;
+
+  if (RuntimeEnabledFeatures::ResourceLoadSchedulerEnabled()) {
+    // If this scheduler is throttled by the associated WebFrameScheduler,
+    // consider every prioritiy as throttable.
+    const auto state = frame_scheduler_throttling_state_;
+    if (state == WebFrameScheduler::ThrottlingState::kThrottled ||
+        state == WebFrameScheduler::ThrottlingState::kStopped) {
+      return true;
+    }
   }
 
-  return true;
+  return priority < ResourceLoadPriority::kMedium;
 }
 
 void ResourceLoadScheduler::OnThrottlingStateChanged(
     WebFrameScheduler::ThrottlingState state) {
+  frame_scheduler_throttling_state_ = state;
   switch (state) {
     case WebFrameScheduler::ThrottlingState::kThrottled:
       if (throttling_history_ == ThrottlingHistory::kInitial)

third_party/WebKit/Source/platform/loader/fetch/ResourceLoadScheduler.h

@@ -187,6 +187,8 @@ class PLATFORM_EXPORT ResourceLoadScheduler final
     kStopped,
   };
   ThrottlingHistory throttling_history_ = ThrottlingHistory::kInitial;
+  WebFrameScheduler::ThrottlingState frame_scheduler_throttling_state_ =
+      WebFrameScheduler::ThrottlingState::kNotThrottled;
 
   // Holds clients that haven't been granted, and are waiting for a grant.
   HeapHashMap<ClientId, Member<ClientWithPriority>> pending_request_map_;