update_engine: fixed warnings from cpplint

Fixed all the cpplint warnings in update engine.

BUG=None
TEST=Unit tests still pass.

Change-Id: I285ae858eec8abe0b26ff203b99a42a200ceb71c
Reviewed-on: https://chromium-review.googlesource.com/204027
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/payload_generator/graph_utils.cc b/payload_generator/graph_utils.cc
index 8b6535d..b3c4231 100644
--- a/payload_generator/graph_utils.cc
+++ b/payload_generator/graph_utils.cc
@@ -133,7 +133,7 @@
     DumpExtents(it->second.write_extents, 6);
   }
 }
-}  // namespace {}
+}  // namespace
 
 void DumpGraph(const Graph& graph) {
   LOG(INFO) << "Graph length: " << graph.size();