gpu: support R16 GPUMemoryBuffer

ui/ozone/platform/drm/common/drm_util.cc

Index: ui/ozone/platform/drm/common/drm_util.cc
diff --git a/ui/ozone/platform/drm/common/drm_util.cc b/ui/ozone/platform/drm/common/drm_util.cc
index 7d35a2a6c252fc4925ce6c3e6e0850518d80b138..02017de0ab78fd53a6bbdaca4bad0e4ab5157aff 100644
--- a/ui/ozone/platform/drm/common/drm_util.cc
+++ b/ui/ozone/platform/drm/common/drm_util.cc
@@ -17,6 +17,11 @@
 #include "base/memory/ptr_util.h"
 #include "ui/display/util/edid_parser.h"
 
+#if !defined(DRM_FORMAT_R16)
+// TODO(riju): after libdrm has this definition, remove it.
+#define DRM_FORMAT_R16 fourcc_code('R', '1', '6', ' ')

[reveman, 2017/06/14 17:47:22]

upstream seems to have this. can we instead just update libdrm in third_party
and on chromeos before we land this?

[riju_, 2017/06/20 13:21:31]

Created bug: https://bugs.chromium.org/p/chromium/issues/detail?id=733703

ChromiumOS CLs:
(libdrm: upgrade): https://chromium-review.googlesource.com/c/539275/
(libpciaccess: upgrade): https://chromium-review.googlesource.com/c/539031/

Not familiar with chromeos package upgrades, so upgraded in wrong overlay.
What I understood from Stéphane Marchesin in 
https://chromium-review.googlesource.com/c/539275/#message-a3485b4a0f5d5d5152...
is that, updating libdrm is already in their plans.
There is already libdrm 2.4.75 in a branch, where some patches have to
rebased/applied and then it would be moved to master.
https://chromium.googlesource.com/chromiumos/third_party/libdrm/+/chromeos-2....,

 
Next Step:
So I suggest we check-in this CL, and I will update DEPS (and fix this TODO)
when libdrm is updated.
This approach was taken in https://codereview.chromium.org/2758013002

+#endif
+
 namespace ui {
 
 namespace {
@@ -363,6 +368,8 @@ int GetFourCCFormatFromBufferFormat(gfx::BufferFormat format) {
   switch (format) {
     case gfx::BufferFormat::R_8:
       return DRM_FORMAT_R8;
+    case gfx::BufferFormat::R_16:
+      return DRM_FORMAT_R16;
     case gfx::BufferFormat::RG_88:
       return DRM_FORMAT_GR88;
     case gfx::BufferFormat::RGBA_8888: