Added a getContentLength() method to URLConnection

This is particularly important if you want to get the number of bytes of a
resource loaded by the class loader:
  getClass().getResource("myFile").openConnection().getContentLength()

classpath/java/net/URL.java

@@ -100,6 +100,10 @@ public final class URL {
       super(url);
     }
 
+    public int getContentLength() {
+      return ResourceInputStream.getContentLength(url.getFile());
+    }
+
     public InputStream getInputStream() throws IOException {
       return new ResourceInputStream(url.getFile());
     }
@@ -116,6 +120,8 @@ public final class URL {
       }
     }
 
+    private static native int getContentLength(String path);
+
     private static native long open(String path) throws IOException;
 
     private static native int read(long peer, int position) throws IOException;