[LiteVideo] Update Media Rebuffer StopThrottle only when allowed.

The LiteVideoObserver observes media rebuffering events and sends
a stop throttling message to the hints agent. This should only
happen if LiteVideos were allowed and a hint sent in the first
place. This also removes the dcheck in the hints agent as
the design changed so the DCHECK is not needed.

Bug: 1125922
Change-Id: I3b65a78acc54bd267ecbabd03e8fd23bea99aad7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398958Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: rajendrant <rajendrant@chromium.org>
Commit-Queue: rajendrant <rajendrant@chromium.org>
Auto-Submit: Michael Crouse <mcrouse@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804953}

chrome/browser/lite_video/lite_video_observer.cc

@@ -245,11 +245,6 @@ void LiteVideoObserver::MediaBufferUnderflow(const content::MediaPlayerId& id) {
   mojo::AssociatedRemote<blink::mojom::PreviewsResourceLoadingHintsReceiver>
       loading_hints_agent;
 
-  if (render_frame_host->GetRemoteAssociatedInterfaces()) {
-    render_frame_host->GetRemoteAssociatedInterfaces()->GetInterface(
-        &loading_hints_agent);
-    loading_hints_agent->StopThrottlingMediaRequests();
-  }
   // Only consider a rebuffer event related to LiteVideos if they
   // were allowed on current navigation.
   if (!nav_metrics_ ||
@@ -257,6 +252,12 @@ void LiteVideoObserver::MediaBufferUnderflow(const content::MediaPlayerId& id) {
     return;
   }
 
+  if (render_frame_host->GetRemoteAssociatedInterfaces()) {
+    render_frame_host->GetRemoteAssociatedInterfaces()->GetInterface(
+        &loading_hints_agent);
+    loading_hints_agent->StopThrottlingMediaRequests();
+  }
+
   nav_metrics_->SetThrottleResult(
       lite_video::LiteVideoThrottleResult::kThrottleStoppedOnRebuffer);
 

chrome/renderer/lite_video/lite_video_hint_agent.cc

@@ -87,12 +87,8 @@ void LiteVideoHintAgent::SetLiteVideoHint(
 }
 
 void LiteVideoHintAgent::StopThrottling() {
-  // TODO(rajendrant): Send the stop throttling signal to browser process, after
-  // some K rebuffer events had occurred.
-  DCHECK(HasLiteVideoHint());
-  for (auto* throttle : active_throttles_) {
+  for (auto* throttle : active_throttles_)
     throttle->ResumeIfThrottled();
-  }
   kilobytes_buffered_before_throttle_ = 0;
 }