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

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

Index: compiler/java/com/google/dart/compiler/ast/DartExprStmt.java
===================================================================
--- compiler/java/com/google/dart/compiler/ast/DartExprStmt.java	(revision 12211)
+++ compiler/java/com/google/dart/compiler/ast/DartExprStmt.java	(working copy)
@@ -20,6 +20,11 @@
   }
 
   @Override
+  public boolean isAbruptCompletingStatement() {
+    return expr instanceof DartThrowExpression;
+  }
+
+  @Override
   public void visitChildren(ASTVisitor<?> visitor) {
     safelyVisitChild(expr, visitor);
   }