Decouple Stopped in bg signal from stop loading experiment.

Make triggering of Stopped in bg signal more generic, it should not be
tied to the experiment to stop loading.
A future CL will trigger a JS callback to indicate stopped to the app. 

Bug: 763573
Change-Id: I439e70fab824d2e243ebfa731d5f27464dc629ff
Reviewed-on: https://chromium-review.googlesource.com/736903
Commit-Queue: Shubhie Panicker <panicker@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Fadi Meawad <fmeawad@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512690}

third_party/WebKit/Source/platform/scheduler/renderer/renderer_scheduler_impl.cc

@@ -1058,6 +1058,8 @@ void RendererSchedulerImpl::UpdatePolicyLocked(UpdateType update_type) {
                          &new_policy_duration);
   }
 
+  bool previously_stopped_when_backgrounded =
+      main_thread_only().stopped_when_backgrounded;
   bool newly_stopped = false;
   if (main_thread_only().renderer_backgrounded &&
       main_thread_only().stopping_when_backgrounded_enabled) {
@@ -1270,9 +1272,11 @@ void RendererSchedulerImpl::UpdatePolicyLocked(UpdateType update_type) {
 
   // TODO(skyostil): send these notifications after releasing the scheduler
   // lock.
-  if (new_policy.loading_queue_policy().is_stopped !=
-      main_thread_only().current_policy.loading_queue_policy().is_stopped) {
-    SetStoppedInBackground(new_policy.loading_queue_policy().is_stopped);
+  if (main_thread_only().stopping_when_backgrounded_enabled) {
+    if (main_thread_only().stopped_when_backgrounded !=
+        previously_stopped_when_backgrounded) {
+      SetStoppedInBackground(main_thread_only().stopped_when_backgrounded);
+    }
   }
 
   if (new_policy.should_disable_throttling() !=

third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc

@@ -528,7 +528,8 @@ void WebFrameSchedulerImpl::UpdateThrottlingState() {
 
 WebFrameScheduler::ThrottlingState
 WebFrameSchedulerImpl::CalculateThrottlingState() const {
-  if (page_stopped_) {
+  if (RuntimeEnabledFeatures::StopLoadingInBackgroundAndroidEnabled() &&
+      page_stopped_) {
     DCHECK(!page_visible_);
     return WebFrameScheduler::ThrottlingState::kStopped;
   }