Cleanup renderStreaming to carry less state

The close method only needs the tail of the template.  Rewrite the
closure so only the tail is retained as UTF-8 encoded bytes, allowing
the JVM to free the larger String.

Use try-with-resources to perform the final write.  This ensures that
if the write fails (e.g.  stream is disconnected), the close still
happens, and the risk of a file descriptor leaking is reduced.

Change-Id: Ia694a3457a386fc311c702472f053d47e670a88c

gitiles-servlet/src/main/java/com/google/gitiles/Renderer.java

diff --git a/gitiles-servlet/src/main/java/com/google/gitiles/Renderer.java b/gitiles-servlet/src/main/java/com/google/gitiles/Renderer.java
index efeef9c..9face08 100644
--- a/gitiles-servlet/src/main/java/com/google/gitiles/Renderer.java
+++ b/gitiles-servlet/src/main/java/com/google/gitiles/Renderer.java
@@ -165,23 +165,20 @@
 
   OutputStream renderStreaming(HttpServletResponse res, String templateName, Map<String, ?> soyData)
       throws IOException {
-    final String html = newRenderer(templateName).setData(soyData).render();
+    String html = newRenderer(templateName).setData(soyData).render();
     int id = html.indexOf(PLACEHOLDER);
     checkArgument(id >= 0, "Template must contain %s", PLACEHOLDER);
 
     int lt = html.lastIndexOf('<', id);
-    final int gt = html.indexOf('>', id + PLACEHOLDER.length());
-    final OutputStream out = res.getOutputStream();
+    int gt = html.indexOf('>', id + PLACEHOLDER.length());
+
+    OutputStream out = res.getOutputStream();
     out.write(html.substring(0, lt).getBytes(UTF_8));
     out.flush();
 
+    byte[] tail = html.substring(gt + 1).getBytes(UTF_8);
     return new OutputStream() {
       @Override
-      public void write(byte[] b) throws IOException {
-        out.write(b);
-      }
-
-      @Override
       public void write(byte[] b, int off, int len) throws IOException {
         out.write(b, off, len);
       }
@@ -198,8 +195,9 @@
 
       @Override
       public void close() throws IOException {
-        out.write(html.substring(gt + 1).getBytes(UTF_8));
-        out.close();
+        try (OutputStream o = out) {
+          o.write(tail);
+        }
       }
     };
   }