ozone: Implement zero/one-copy texture for Ozone GBM.

ui/ozone/platform/drm/gbm.gypi

Index: ui/ozone/platform/drm/gbm.gypi
diff --git a/ui/ozone/platform/drm/gbm.gypi b/ui/ozone/platform/drm/gbm.gypi
index 36074bb2fd583725e08e5449e58298b21ade2b9d..5a6d79cac29953509b4f6af4a49f7ffa3b279951 100644
--- a/ui/ozone/platform/drm/gbm.gypi
+++ b/ui/ozone/platform/drm/gbm.gypi
@@ -11,6 +11,7 @@
       'gbm',
     ],
     'use_mesa_platform_null%': 0,
+    'ozone_use_vgem_map%': 0,

[reveman, 2015/08/07 14:35:16]

just to be sure I understand. we have hardware that use gbm but doesn't support
vgem yet, correct? in that case, can you add a TODO about removing this flag
when all gbm hardware support vgem?

[vignatti (out of this project), 2015/08/07 14:51:25]

correct, but I don't think it's about hardware only or its driver supporting
dma-buf userspace mmap etc.

It's more about CrOS vs other Linux and their graphics subsystem allocator of
choice. For example, we were shipping out a Web view based on Ozone-GBM running
on Yocto, which doesn't have VGEM at all. So atm I think it's more about
choosing a graphics module, testing it, consolidate the implementation, decide
which is the one and so on.

[dshwang, 2015/08/07 15:36:46]

correct. Done.

   },
   'targets': [
     {
@@ -54,6 +55,13 @@
         ['use_mesa_platform_null==1', {
           'defines': ['USE_MESA_PLATFORM_NULL'],
         }],
+        ['ozone_use_vgem_map==1', {
+          'defines': ['OZONE_USE_VGEM_MAP'],
+          'sources': [
+            'gpu/client_native_pixmap_vgem.cc',
+            'gpu/client_native_pixmap_vgem.h',
+          ],
+        }],
       ],
     },
   ],