Fixed scroll focused smoothness metric

The scroll focused smoothness metric would report smoothness as usual when no scrolling is active.

Bug: chromium:1278778
Change-Id: I0c19271df3e9095c19bb328ce9c48a5ab5ad3bf3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3330481
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Commit-Queue: Behdad Bakhshinategh <behdadb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#950609}

cc/metrics/dropped_frame_counter.cc

@@ -592,7 +592,7 @@ void DroppedFrameCounter::UpdateDroppedFrameCountInWindow(
     dropped_frame_count_in_window_[SmoothnessStrategy::kMainFocusedStrategy] +=
         count;
   }
-  if (frame_info.WasScrollUpdateDropped()) {
+  if (frame_info.IsScrollPrioritizeFrameDropped()) {
     DCHECK_GE(dropped_frame_count_in_window_
                       [SmoothnessStrategy::kScrollFocusedStrategy] +
                   count,

cc/metrics/frame_info.cc

@@ -163,14 +163,17 @@ bool FrameInfo::WasMainUpdateDropped() const {
   return false;
 }
 
-bool FrameInfo::WasScrollUpdateDropped() const {
+bool FrameInfo::IsScrollPrioritizeFrameDropped() const {
+  // If any scroll is active the dropped frame for only the scrolling thread is
+  // reported. If no scroll is active then reports if dropped frames is
+  // affecting smoothness.
   switch (scroll_thread) {
     case SmoothEffectDrivingThread::kCompositor:
       return WasCompositorUpdateDropped();
     case SmoothEffectDrivingThread::kMain:
       return WasMainUpdateDropped();
     case SmoothEffectDrivingThread::kUnknown:
-      return false;
+      return IsDroppedAffectingSmoothness();
   }
 }
 

cc/metrics/frame_info.h

@@ -68,7 +68,7 @@ struct CC_EXPORT FrameInfo {
 
   bool WasCompositorUpdateDropped() const;
   bool WasMainUpdateDropped() const;
-  bool WasScrollUpdateDropped() const;
+  bool IsScrollPrioritizeFrameDropped() const;
 
  private:
   bool was_merged = false;