Add another missing dependency

travis/setup.sh

diff --git a/travis/setup.sh b/travis/setup.sh
index 367d9f2..d25c55c 100755
--- a/travis/setup.sh
+++ b/travis/setup.sh
@@ -13,7 +13,7 @@
 export PATH="$(pwd)/depot_tools:${PATH}"
 
 # Get dependencies.
-sudo apt-get install libdbus-1-dev libgconf2-dev bison gperf wdiff python-openssl
+sudo apt-get install libdbus-1-dev libgconf2-dev bison gperf wdiff python-openssl libxtst-dev
 sudo easy_install pip
 sudo pip install requests