Consistently type check analysis server request parameters.

pkg/analysis_server/test/domain_context_test.dart

Index: pkg/analysis_server/test/domain_context_test.dart
diff --git a/pkg/analysis_server/test/domain_context_test.dart b/pkg/analysis_server/test/domain_context_test.dart
index 10421c73d4d952e33b9a9084a2b92af0a533b761..358aea07bb02fa41fa300b678b9a44a519e27b3e 100644
--- a/pkg/analysis_server/test/domain_context_test.dart
+++ b/pkg/analysis_server/test/domain_context_test.dart
@@ -36,6 +36,7 @@ class ContextDomainHandlerTest {
 
     Request request = new Request('0', ContextDomainHandler.APPLY_CHANGES_NAME);
     request.setParameter(ContextDomainHandler.CONTEXT_ID_PARAM, contextId);
+    request.setParameter(ContextDomainHandler.SOURCES_PARAM, []);
     request.setParameter(ContextDomainHandler.CHANGES_PARAM, {
       ContextDomainHandler.ADDED_PARAM : ['ffile:/one.dart'],
       ContextDomainHandler.MODIFIED_PARAM : ['ffile:/two.dart'],
@@ -53,11 +54,13 @@ class ContextDomainHandlerTest {
     Request request = new Request('0', ContextDomainHandler.APPLY_CHANGES_NAME);
     ContextDomainHandler handler = new ContextDomainHandler(server);
     SourceFactory sourceFactory = new SourceFactory([new FileUriResolver()]);
-    ChangeSet changeSet = handler.createChangeSet(request, sourceFactory, {
-      ContextDomainHandler.ADDED_PARAM : ['ffile:/one.dart'],
-      ContextDomainHandler.MODIFIED_PARAM : [],
-      ContextDomainHandler.REMOVED_PARAM : ['ffile:/two.dart', 'ffile:/three.dart']
-    });
+    ChangeSet changeSet = handler.createChangeSet(request, sourceFactory,
+        new RequestDatum(request, ContextDomainHandler.CHANGES_PARAM, {
+      ContextDomainHandler.ADDED_PARAM: ['ffile:/one.dart'],
+      ContextDomainHandler.MODIFIED_PARAM: [],
+      ContextDomainHandler.REMOVED_PARAM: ['ffile:/two.dart',
+          'ffile:/three.dart']
+    }));
     expect(changeSet.addedSources, hasLength(equals(1)));
     expect(changeSet.changedSources, hasLength(equals(0)));
     expect(changeSet.removedSources, hasLength(equals(2)));