Insert a blank line before and after classes.

test/whitespace/compilation_unit.unit

 40 columns                              |
 >>> discard newlines before library
 
 
 library a;
 <<<
 library a;
 >>> discard newlines before first import
 
 
@@ skipping 43 matching lines @@
 
 
 <<<
 class A {}
 
 class B = Base with Mixin;
 
 var c = 1;
 
 d() {}
->>> require at least a single newline between declarations
-class A {} class B = Base with Mixin; var c = 1; d() {}
-<<<
-class A {}
-class B = Base with Mixin;
-var c = 1;
-d() {}
 >>> force two newlines between directives and declarations
 library a; var b;
 <<<
 library a;
 
 var b;
 >>> dartbug.com/15912
 abstract class A = B with C<E>;
 <<<
-abstract class A = B with C<E>;
+abstract class A = B with C<E>;
+>>> blank line between classes
+class A {} class B {}
+<<<
+class A {}
+
+class B {}
+>>> blank line between variables and classes
+var a = 1; class B{} var c = 3;
+<<<
+var a = 1;
+
+class B {}
+
+var c = 3;
+>>> blank line between functions and classes
+a() {} class B{} c() {}
+<<<
+a() {}
+
+class B {}
+
+c() {}
+>>> require newline between non-class declarations
+var a = 1; var b = 1; c() {} d() {} var e = 1;
+<<<
+var a = 1;
+var b = 1;
+c() {}
+d() {}
+var e = 1;