Remove unreferenced member of Renderer11, mDepthStencilInitialized.
Remove unreferenced member of Renderer11, mDepthStencilInitialized.

BUG=angleproject:1260

Change-Id: I3773297a4e517e2fca7072f56f3bdbec0a561d9a
Reviewed-on: https://chromium-review.googlesource.com/326851
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

ecoal95/angle,ppy/angle,MSOpenTech/angle,ecoal95/angle,mikolalysenko/angle,ppy/angle,ecoal95/angle,domokit/waterfall,ecoal95/angle,domokit/waterfall,MSOpenTech/angle,ppy/angle,ppy/angle,mikolalysenko/angle,ecoal95/angle,mikolalysenko/angle,MSOpenTech/angle,mikolalysenko/angle,MSOpenTech/angle