Make the TestServer use an absolute document root path.

net/test/remote_test_server.h

Index: net/test/remote_test_server.h
diff --git a/net/test/remote_test_server.h b/net/test/remote_test_server.h
index 9c3fcfc2c1d9101be733147eee3d9a1478505e55..43136a0ca3693cb1dc8a4334b89b82d26980f62a 100644
--- a/net/test/remote_test_server.h
+++ b/net/test/remote_test_server.h
@@ -18,7 +18,8 @@ class SpawnerCommunicator;
 class RemoteTestServer : public BaseTestServer {
  public:
   // Initialize a TestServer listening on a specific host (IP or hostname).
-  // |document_root| must be a relative path under the root tree.
+  // |document_root| must be an absolute paht, or a relative path under the
+  // source directory.
   RemoteTestServer(Type type,
                    const std::string& host,
                    const FilePath& document_root);