extract LibraryMemberContributor from prefixed element contributor

pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart

Index: pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
diff --git a/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart b/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
index f8f064c23cd993c536c5b9814f4905522aa01665..d85c23da2c2fd3d90b307a10da9d9a4ceb5aebe7 100644
--- a/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
+++ b/pkg/analysis_server/test/services/completion/prefixed_element_contributor_test.dart
@@ -219,7 +219,8 @@ void f(C<int> c) {
     // SimpleIdentifier  PrefixedIdentifier  ExpressionStatement
     addTestSource('import "dart:async" as bar; foo() {bar.^}');
     return computeFull((bool result) {
-      assertSuggestClass('Future');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('Future');
       assertNotSuggested('loadLibrary');
     });
   }
@@ -228,7 +229,8 @@ void f(C<int> c) {
     // SimpleIdentifier  MethodInvocation  ExpressionStatement
     addTestSource('import "dart:async" as bar; foo() {bar.^ print("f")}');
     return computeFull((bool result) {
-      assertSuggestClass('Future');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('Future');
     });
   }
 
@@ -236,8 +238,9 @@ void f(C<int> c) {
     // SimpleIdentifier  MethodInvocation  ExpressionStatement
     addTestSource('import "dart:async" as bar; foo() {new bar.F^ print("f")}');
     return computeFull((bool result) {
-      assertSuggestConstructor('Future');
-      assertSuggestConstructor('Future.delayed');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('Future');
+      assertNotSuggested('Future.delayed');
     });
   }
 
@@ -245,8 +248,9 @@ void f(C<int> c) {
     // SimpleIdentifier  PrefixedIdentifier  ExpressionStatement
     addTestSource('import "dart:async" deferred as bar; foo() {bar.^}');
     return computeFull((bool result) {
-      assertSuggestClass('Future');
-      assertSuggestFunction('loadLibrary', 'Future<dynamic>');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('Future');
+      assertNotSuggested('loadLibrary');
     });
   }
 
@@ -256,8 +260,9 @@ void f(C<int> c) {
     addTestSource('import "/libB.dart" as foo; main() {foo.^} class C { }');
     computeFast();
     return computeFull((bool result) {
-      assertSuggestClass('B');
-      assertSuggestClass('A');
+      // Suggested by LibraryMemberContributor
+      assertNotSuggested('B');
+      assertNotSuggested('A');
     });
   }