Document one argument per line for constructor injection

Change-Id: I4a698f6a3a1d601b691463ceaaeab407901c6a9d
diff --git a/Documentation/dev-contributing.txt b/Documentation/dev-contributing.txt
index c1f398f..72d7ddf 100644
--- a/Documentation/dev-contributing.txt
+++ b/Documentation/dev-contributing.txt
@@ -221,6 +221,7 @@
     should be before the instance members.
   * Annotations should go before language keywords (`final`, `private`, etc) +
     Example: `@Assisted @Nullable final type varName`
+  * The `@Inject`-ed constructor arguments should be listed one per line.
   * Imports should be mostly alphabetical (uppercase sorts before
     all lowercase, which means classes come before packages at the
     same level).