Convert throw from a statement to an expression (issue 4872)

compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java

Index: compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java	(revision 12211)
+++ compiler/java/com/google/dart/compiler/ast/DartToSourceVisitor.java	(working copy)
@@ -575,14 +575,12 @@
   }
 
   @Override
-  public Void visitThrowStatement(DartThrowStatement x) {
+  public Void visitThrowExpression(DartThrowExpression x) {
     p("throw");
     if (x.getException() != null) {
       p(" ");
       accept(x.getException());
     }
-    p(";");
-    nl();
     return null;
   }