Merge branch 'master' into ph-trusty-to-xenial

Author: Pezi777

user/gui-and-headless-browsers.md

@@ -195,7 +195,8 @@ Headless mode can be enabled using the `MOZ_HEADLESS`
 
 ```yaml
 env:
-  - MOZ_HEADLESS=1
+  global:
+    - MOZ_HEADLESS=1
 addons:
   firefox: latest
 ```

user/languages/dart.md

@@ -34,7 +34,7 @@ This guide covers build environment and configuration topics specific to
 Travis CI support for Dart is contributed by the community and may be removed
 or altered at any time. If you run into any problems, please report them in the
 [Travis CI issue tracker](https://github.com/travis-ci/travis-ci/issues/new?labels=community:dart)
-and cc [@nex3](https://github.com/nex3) and [@a14n](https://github.com/a14n).
+and cc [@athomas](https://github.com/athomas) and [@a14n](https://github.com/a14n).
 
 ## Choosing Dart versions to test against
 

user/languages/java.md

@@ -195,8 +195,8 @@ details.
 
 The list of available JVMs for different dists are at
 
-  * [JDKs installed for **Bionic**](/user/reference/bionic/#jvm-clojure-groovy-java-scala-images)
-  * [JDKs installed for **Xenial**](/user/reference/xenial/#jvm-clojure-groovy-java-scala-images)
+  * [JDKs installed for **Bionic**](/user/reference/bionic/#jvm-clojure-groovy-java-scala-support)
+  * [JDKs installed for **Xenial**](/user/reference/xenial/#jvm-clojure-groovy-java-scala-support)
   * [JDKs installed for **Trusty**](/user/reference/trusty/#jvm-clojure-groovy-java-scala-images)
   * [JDKs installed for **Precise**](/user/reference/precise/#jvm-clojure-groovy-java-scala-vm-images)
 

user/reference/linux.md

@@ -11,8 +11,8 @@ This page gives an overview of the different Ubuntu Linux distributions you can
 You can choose one of the following distributions:
 
 * [Ubuntu Bionic 18.04](/user/reference/bionic/)
-* [Ubuntu Xenial 16.04](/user/reference/xenial/)
-* [Ubuntu Trusty 14.04](/user/reference/trusty/) **default**
+* [Ubuntu Xenial 16.04](/user/reference/xenial/) **default**
+* [Ubuntu Trusty 14.04](/user/reference/trusty/) 
 * [Ubuntu Precise 12.04](/user/reference/precise/)
 
 Travis CI also supports the [Windows Build Environment](/user/reference/windows/) and [macOS Build Environment](/user/reference/osx/).