Tweak opacity for timeline flame chart section labels (#2088)

* Tweak opacity for timeline flame chart section labels

packages/devtools_app/lib/src/timeline/timeline_flame_chart.dart

diff --git a/packages/devtools_app/lib/src/timeline/timeline_flame_chart.dart b/packages/devtools_app/lib/src/timeline/timeline_flame_chart.dart
index 53bd8bc..edfe129 100644
--- a/packages/devtools_app/lib/src/timeline/timeline_flame_chart.dart
+++ b/packages/devtools_app/lib/src/timeline/timeline_flame_chart.dart
@@ -496,11 +496,11 @@
         eventGroups.values.toList().indexOf(group),
         isDarkTheme: isDarkTheme,
       );
-      final backgroundWithAlpha = Color.fromRGBO(
+      final backgroundWithOpacity = Color.fromRGBO(
         backgroundColor.red,
         backgroundColor.green,
         backgroundColor.blue,
-        0.75,
+        0.85,
       );
 
       canvas.drawRect(
@@ -510,7 +510,7 @@
           labelWidth,
           rowHeightWithPadding,
         ),
-        Paint()..color = backgroundWithAlpha,
+        Paint()..color = backgroundWithOpacity,
       );
 
       textPainter.paint(

packages/devtools_app/test/goldens/timeline_flame_chart_with_selected_frame.png

diff --git a/packages/devtools_app/test/goldens/timeline_flame_chart_with_selected_frame.png b/packages/devtools_app/test/goldens/timeline_flame_chart_with_selected_frame.png
index 3258b3c..e5fc3d3 100644
--- a/packages/devtools_app/test/goldens/timeline_flame_chart_with_selected_frame.png
+++ b/packages/devtools_app/test/goldens/timeline_flame_chart_with_selected_frame.png
Binary files differ