Update GCE discovery documentation

(cherry picked from commit d4cb81c)
(cherry picked from commit 9af04eb)
(cherry picked from commit b383344)

docs/plugins/cloud-gce.asciidoc

@@ -129,7 +129,7 @@ scopes=compute-rw
 --------------------------------------------------
 
 Failing to set this will result in unauthorized messages when starting Elasticsearch.
-See [Machine Permissions](#machine-permissions).
+See <<cloud-gce-usage-discovery-tips-permissions>>.
 ==============================================
 
 
@@ -142,8 +142,15 @@ sudo apt-get update
 # Download Elasticsearch
 wget https://download.elasticsearch.org/elasticsearch/elasticsearch/elasticsearch-2.0.0.deb
 
-# Prepare Java installation
-sudo apt-get install java8-runtime-headless
+# Prepare Java installation (Oracle)
+sudo echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main" | sudo tee /etc/apt/sources.list.d/webupd8team-java.list
+sudo echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main" | sudo tee -a /etc/apt/sources.list.d/webupd8team-java.list
+sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys EEA14886
+sudo apt-get update
+sudo apt-get install oracle-java8-installer
+
+# Prepare Java installation (or OpenJDK)
+# sudo apt-get install java8-runtime-headless
 
 # Prepare Elasticsearch installation
 sudo dpkg -i elasticsearch-2.0.0.deb
@@ -221,7 +228,7 @@ First create an image of your running instance and upload it to Google Cloud Sto
 
 [source,sh]
 --------------------------------------------------
-# Create an image of yur current instance
+# Create an image of your current instance
 sudo /usr/bin/gcimagebundle -d /dev/sda -o /tmp/
 
 # An image has been created in `/tmp` directory: