Completion. Cache 'inConstantContext' value.

For package:collection, computing measures.

Before: 0:01:00.236000
After:  0:00:55.977000

So, about 7% faster.
I think this translates into actual completion speed up.

Change-Id: I45f0c0186d5988e6e1b043d465030668cd61335b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/357982
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: scheglov

pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart

@@ -290,6 +290,12 @@ class DartCompletionRequest {
 
   bool _aborted = false;
 
+  /// Return `true` if the completion is occurring in a constant context.
+  late final bool inConstantContext = () {
+    var entity = target.entity;
+    return entity is Expression && entity.inConstantContext;
+  }();
+
   factory DartCompletionRequest({
     required AnalysisSession analysisSession,
     required String filePath,
@@ -387,12 +393,6 @@ class DartCompletionRequest {
     return opType.includeIdentifiers;
   }
 
-  /// Return `true` if the completion is occurring in a constant context.
-  bool get inConstantContext {
-    var entity = target.entity;
-    return entity is Expression && entity.inConstantContext;
-  }
-
   InheritanceManager3 get inheritanceManager {
     return analysisSession.inheritanceManager;
   }

pkg/analysis_server/tool/code_completion/completion_metrics_base.dart

@@ -120,6 +120,11 @@ abstract class CompletionMetricsComputer {
     final results = <ResolvedUnitResult>[];
     final pathContext = context.contextRoot.resourceProvider.pathContext;
     for (final filePath in context.contextRoot.analyzedFiles()) {
+      if (file_paths.isGenerated(filePath) ||
+          filePath.endsWith('animated_icons.dart') ||
+          filePath.endsWith('animated_icons_data.dart')) {
+        continue;
+      }
       if (file_paths.isDart(pathContext, filePath)) {
         try {
           final result = await context.currentSession.getResolvedUnit(filePath)