We really don't require openbox to build Flutter. (flutter#121)

Author: Hixie

build/install-build-deps.sh

@@ -96,7 +96,7 @@ dev_list="bison cdbs curl dpkg-dev elfutils devscripts fakeroot
           libglu1-mesa-dev libgnome-keyring-dev libgtk2.0-dev libkrb5-dev
           libnspr4-dev libnss3-dev libpam0g-dev libpci-dev libpulse-dev
           libsctp-dev libspeechd-dev libsqlite3-dev libssl-dev libudev-dev
-          libwww-perl libxslt1-dev libxss-dev libxt-dev libxtst-dev openbox
+          libwww-perl libxslt1-dev libxss-dev libxt-dev libxtst-dev
           patch perl pkg-config python python-cherrypy3 python-crypto
           python-dev python-numpy python-opencv python-openssl python-psutil
           python-yaml rpm ruby subversion wdiff zip"