Update the docker image to use Debian stretch

Change-Id: I91695573303f670960eb7302c1afe9c501d17d5a

tools/docker/image/Dockerfile

diff --git a/tools/docker/image/Dockerfile b/tools/docker/image/Dockerfile
index a308e46..79cfac0 100644
--- a/tools/docker/image/Dockerfile
+++ b/tools/docker/image/Dockerfile
@@ -1,9 +1,7 @@
 # Copyright (c) 2017, the R8 project authors. Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
-FROM debian:jessie
-
-RUN echo deb http://http.debian.net/debian jessie-backports main >> /etc/apt/sources.list
+FROM debian:stretch
 
 RUN apt-get update && apt-get install -y \
 	bzip2 \
@@ -17,12 +15,9 @@
 	texinfo \
 	unzip \
 	wget \
+        openjdk-8-jdk \
     sudo
 
-# Install OpenJDK 8 dependencies from jessi-backports (see https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=851667)
-RUN apt-get install -y -t jessie-backports openjdk-8-jre-headless ca-certificates-java
-RUN apt-get install -y openjdk-8-jdk
-
 # Set the timezone.
 RUN echo "Europe/Copenhagen" > /etc/timezone && \
     dpkg-reconfigure -f noninteractive tzdata