Update some of the fixes to use ChangeBuilder

pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart

Index: pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
diff --git a/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart b/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
index 6ce511f8ff170230ee601b8cdabf224badcdec4c..b1a48551789547ba77284b44c9edaa42a7a1c770 100644
--- a/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
+++ b/pkg/analyzer_plugin/lib/src/utilities/change_builder/change_builder_dart.dart
@@ -1012,7 +1012,11 @@ class DartFileEditBuilderImpl extends FileEditBuilderImpl
         type is InterfaceType && type.element == futureType.element) {
       return;
     }
-    futureType = futureType.instantiate(<DartType>[type]);
+    // TODO(brianwilkerson) Unconditionally execute the body of the 'if' when
+    // Future<void> is fully supported.
+    if (!type.isVoid) {

[scheglov, 2017/05/26 16:30:04]

Use Future<Null> instead of Future<void> for now?

[Brian Wilkerson, 2017/05/30 13:15:12]

If this is important, I can fix it in a follow-up CL.

+      futureType = futureType.instantiate(<DartType>[type]);
+    }
     // prepare code for the types
     addReplacement(range.node(typeAnnotation), (EditBuilder builder) {
       if (!(builder as DartEditBuilder).writeType(futureType)) {
@@ -1123,8 +1127,8 @@ class DartFileEditBuilderImpl extends FileEditBuilderImpl
   }
 
   /**
-   * Returns a [InsertDesc] describing where to insert a new directive or a
-   * top-level declaration at the top of the file.
+   * Returns an insertion description describing where to insert a new directive
+   * or a top-level declaration at the top of the file.
    */
   _InsertionDescription _getInsertDescTop() {
     // skip leading line comments
@@ -1168,7 +1172,7 @@ class DartFileEditBuilderImpl extends FileEditBuilderImpl
     }
     // determine if empty line is required after
     int currentLine = lineInfo.getLocation(offset).lineNumber;
-    if (currentLine < lineInfo.lineCount) {
+    if (currentLine + 1 < lineInfo.lineCount) {
       int nextLineOffset = lineInfo.getOffsetOfLine(currentLine + 1);
       String insertLine = source.substring(offset, nextLineOffset);
       if (!insertLine.trim().isEmpty) {