Fix for subscribing for notifications for files in packages.

pkg/analysis_server/lib/src/domain_completion.dart

Index: pkg/analysis_server/lib/src/domain_completion.dart
diff --git a/pkg/analysis_server/lib/src/domain_completion.dart b/pkg/analysis_server/lib/src/domain_completion.dart
index e6bb3282603aa42b065c3da5178505f88b2e28fc..affe17c46e87a27371072af69648e3c5025594a1 100644
--- a/pkg/analysis_server/lib/src/domain_completion.dart
+++ b/pkg/analysis_server/lib/src/domain_completion.dart
@@ -174,8 +174,9 @@ class CompletionDomainHandler implements RequestHandler {
         new CompletionGetSuggestionsParams.fromRequest(request);
     // schedule completion analysis
     String completionId = (_nextCompletionId++).toString();
-    AnalysisContext context = server.getAnalysisContext(params.file);
-    Source source = server.getSource(params.file);
+    ContextSourcePair contextSource = server.getContextSourcePair(params.file);
+    AnalysisContext context = contextSource.context;
+    Source source = contextSource.source;
     recordRequest(performance, context, source, params.offset);
     if (manager == null) {
       manager = completionManagerFor(context, source);