Constructor initializer indent fixes.

pkg/analyzer/test/services/data/cu_tests.data

 >>>
 class
 A
 {
 }
 <<<
 class A {
 }
 >>> dartbug.com/15876
 // fisk
@@ skipping 195 matching lines @@
 <<<
 class A extends B {}
 >>>
 class A extends B {
 
 }
 <<<
 class A extends B {
 
 }
+>>> Single initializers can be on one line
+class Foo extends Bar {
+  final int b;
+  Foo(int a, this.b): super(a);
+}
+<<<
+class Foo extends Bar {
+  final int b;
+  Foo(int a, this.b): super(a);
+}
+>>> (or not)
+class Foo extends Bar {
+  final int b;
+  Foo(int a, this.b)
+      : super(a);
+}
+<<<
+class Foo extends Bar {
+  final int b;
+  Foo(int a, this.b)
+      : super(a);
+}
+>>> Multiple initializers are one per line
+class Foo extends Bar {
+  final int b;
+  Foo(int a, int b) : super(a), this.b = b == null ? 0 : b;
+}
+<<<
+class Foo extends Bar {
+  final int b;
+  Foo(int a, int b)
+      : super(a),
+        this.b = b == null ? 0 : b;
+}