ui: Add gfx::BufferUsage::SCANOUT_CPU_READ_WRITE.

ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc

Index: ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
diff --git a/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc b/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
index 6199e36f11a432930ad3987441a5b8425c805770..3fd704df7684f8b08f7a712fe78a757d9c2508f7 100644
--- a/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
+++ b/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
@@ -57,6 +57,11 @@ class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
       case gfx::BufferUsage::SCANOUT:
         return format == gfx::BufferFormat::BGRX_8888 ||
                format == gfx::BufferFormat::RGBX_8888;
+      case gfx::BufferUsage::SCANOUT_CPU_READ_WRITE:
+        return format == gfx::BufferFormat::BGRX_8888 ||
+               format == gfx::BufferFormat::BGRA_8888 ||
+               format == gfx::BufferFormat::RGBX_8888 ||
+               format == gfx::BufferFormat::RGBA_8888;
       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE:
       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT: {
 #if defined(OS_CHROMEOS)
@@ -82,6 +87,7 @@ class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
       gfx::BufferUsage usage) override {
     DCHECK(!handle.fds.empty());
     switch (usage) {
+      case gfx::BufferUsage::SCANOUT_CPU_READ_WRITE:

[dcheng, 2017/02/27 23:14:56]

Quick question: are these only supposed to be used on CrOS?

[reveman, 2017/02/27 23:47:23]

They can be used on other platforms too. The scanout ones might not make as much
sense on other platforms today but they should still work.

       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE:
       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT:
 #if defined(OS_CHROMEOS)