Mention commit access (#7232)

CONTRIBUTING.md

@@ -3,6 +3,8 @@ Contributing to Flutter
 
 [![Build Status](https://travis-ci.org/flutter/flutter.svg)](https://travis-ci.org/flutter/flutter)
 
+_See also: [Flutter's code of conduct](https://flutter.io/design-principles/#code-of-conduct)_
+
 Things you will need
 --------------------
 
@@ -124,9 +126,6 @@ To send us a pull request:
   "Compare & pull request" button
 
 Please make sure all your checkins have detailed commit messages explaining the patch.
-If you made multiple commits for a single pull request, either make sure each one has a detailed
-message explaining that specific commit, or squash your commits into one single checkin with a
-detailed message before sending the pull request.
 
 Once you've gotten an LGTM from a project maintainer, submit your changes to the
 `master` branch using one of the following methods:
@@ -142,6 +141,9 @@ You can do this online, and it only takes a minute.
 If you've never submitted code before, you must add your (or your
 organization's) name and contact info to the [AUTHORS](AUTHORS) file.
 
+We grant commit access to people who have gained our trust and demonstrated
+a commitment to Flutter.
+
 Tools for tracking an improving test coverage
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