Use std::tie() for operator< in content/

Simplify the code for operator< when comparing multiple members using
a common std::tie idiom.

BUG=555171
[email protected]

Review URL: https://codereview.chromium.org/1462213002

Cr-Commit-Position: refs/heads/master@{#360883}
diff --git a/content/browser/host_zoom_map_impl.h b/content/browser/host_zoom_map_impl.h
index a9b2a45..dbf166a 100644
--- a/content/browser/host_zoom_map_impl.h
+++ b/content/browser/host_zoom_map_impl.h
@@ -7,6 +7,7 @@
 
 #include <map>
 #include <string>
+#include <tuple>
 #include <vector>
 
 #include "base/compiler_specific.h"
@@ -112,9 +113,8 @@
         : render_process_id(render_process_id),
           render_view_id(render_view_id) {}
     bool operator<(const RenderViewKey& other) const {
-      return render_process_id < other.render_process_id ||
-             ((render_process_id == other.render_process_id) &&
-              (render_view_id < other.render_view_id));
+      return std::tie(render_process_id, render_view_id) <
+             std::tie(other.render_process_id, other.render_view_id);
     }
   };