Issue 1177: Non-existant documentation directory throws

compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java

Index: compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java
diff --git a/compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java b/compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java
index d2bda84f441ec348d0c27fd6f1dc8fe03205dac3..b80af3ff2239fbb5ae03f7b9bc067820ea6b66de 100644
--- a/compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java
+++ b/compiler/java/com/google/dart/compiler/backend/doc/DartDocumentationVisitor.java
@@ -623,9 +623,10 @@ class DartDocumentationVisitor extends DartNodeTraverser<Void> {
     if (isPrivateName(name)) {
       return;
     }
-    String fileName = outputDirectory + File.separator + name + ".html";
     try {
-      stream = new PrintStream(fileName);
+      File output = new File(outputDirectory, name + ".html");
+      output.getParentFile().mkdirs();
+      stream = new PrintStream(output);
     } catch (FileNotFoundException e) {
       throw new RuntimeException(e);
     }