metrics: Fix Some Display Issues in Perf Metrics HUD

This CL fixes two things: it removes the perf metrics HUD in iframes,
and it stops flashing of metrics in some cases.

R=sadrul

Change-Id: I0b6603600c48bffbe6229a11f8798b0bb6ec31d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601218Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: weiliangc <weiliangc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839794}

cc/layers/heads_up_display_layer.cc

@@ -91,7 +91,7 @@ void HeadsUpDisplayLayer::PushPropertiesTo(LayerImpl* layer) {
   layer_impl->SetHUDTypeface(typeface_);
   layer_impl->SetLayoutShiftRects(layout_shift_rects_);
   layout_shift_rects_.clear();
-  if (web_vital_metrics_)
+  if (web_vital_metrics_ && web_vital_metrics_->HasValue())
     layer_impl->SetWebVitalMetrics(std::move(web_vital_metrics_));
 }
 

cc/layers/heads_up_display_layer_impl.cc

@@ -567,7 +567,8 @@ void HeadsUpDisplayLayerImpl::PushPropertiesTo(LayerImpl* layer) {
   layer_impl->SetHUDTypeface(typeface_);
   layer_impl->SetLayoutShiftRects(layout_shift_rects_);
   layout_shift_rects_.clear();
-  layer_impl->SetWebVitalMetrics(std::move(web_vital_metrics_));
+  if (web_vital_metrics_ && web_vital_metrics_->HasValue())
+    layer_impl->SetWebVitalMetrics(std::move(web_vital_metrics_));
 }
 
 void HeadsUpDisplayLayerImpl::UpdateHudContents() {

third_party/blink/renderer/core/frame/web_frame_widget_impl.cc

@@ -2131,6 +2131,10 @@ std::unique_ptr<cc::WebVitalMetrics> WebFrameWidgetImpl::GetWebVitalMetrics() {
                             .WeightedScore();
   if (layout_shift > 0.f)
     metrics->layout_shift = layout_shift;
+
+  if (!metrics->HasValue())
+    return nullptr;
+
   return metrics;
 }
 

third_party/blink/renderer/platform/widget/compositing/layer_tree_settings.cc

@@ -360,10 +360,12 @@ cc::LayerTreeSettings GenerateLayerTreeSettings(
       cmd.HasSwitch(cc::switches::kHighlightNonLCDTextLayers);
   settings.initial_debug_state.show_web_vital_metrics =
       base::FeatureList::IsEnabled(
-          ::features::kHudDisplayForPerformanceMetrics);
+          ::features::kHudDisplayForPerformanceMetrics) &&
+      !for_child_local_root_frame;
   settings.initial_debug_state.show_smoothness_metrics =
       base::FeatureList::IsEnabled(
-          ::features::kHudDisplayForPerformanceMetrics);
+          ::features::kHudDisplayForPerformanceMetrics) &&
+      !for_child_local_root_frame;
 
   settings.initial_debug_state.SetRecordRenderingStats(
       cmd.HasSwitch(cc::switches::kEnableGpuBenchmarking));