Fix Linux link errors for some targets by adding -lX11 to gpu.gyp's dependencies.
Fix Linux link errors for some targets by adding -lX11 to gpu.gyp's
dependencies.

Broken out and landed separately from  https://codereview.appspot.com/6826086/

git-svn-id: e8541e15acce502a64c929015570ad1648e548cd@6388 2bbb7eff-a529-9590-31e7-b0007b416f81

Cue/skia,Cue/skia,Cue/skia,Cue/skia