[Ozone-DRM] Fix msan error of use of uninitialized memory

BUG=855580
TEST=Compiled and ran ozone_unittests with msan

Change-Id: I9f2d42b98210f9edca33d6d5defcae0ed29f1a07
Reviewed-on: https://chromium-review.googlesource.com/1111977Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569615}

ui/ozone/platform/drm/gpu/crtc_controller.h

@@ -100,7 +100,7 @@ class CrtcController : public base::SupportsWeakPtr<CrtcController> {
   // TODO(dnicoara) Add support for hardware mirroring (multiple connectors).
   uint32_t connector_;
 
-  drmModeModeInfo mode_;
+  drmModeModeInfo mode_ = {};
 
   // Keeps track of the CRTC state. If a surface has been bound, then the value
   // is set to false. Otherwise it is true.