Ozone GBM: support R_8 format to GpuMemoryBuffers

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 3e32b7ff1321ace84b3093655ecb6279905641de..ce5c85bac200b446973c421268199e7011670ffc 100644
--- a/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
+++ b/ui/ozone/platform/drm/client_native_pixmap_factory_gbm.cc
@@ -49,7 +49,13 @@ class ClientNativePixmapFactoryGbm : public ClientNativePixmapFactory {
       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE:
       case gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT: {
 #if defined(OS_CHROMEOS)
-        return format == gfx::BufferFormat::BGRA_8888;
+        return
+#if defined(ARCH_CPU_X86_FAMILY)
+            // Currently only i915 in the driver (i.e. minigbm and Mesa)
+            // supports R_8. crbug.com/356871
+            format == gfx::BufferFormat::R_8 ||

[dshwang, 2016/05/04 07:28:36]

narrow R_8 support to only Intel architecture, because only Intel driver
supports R_8 unlike BGRA_8888, which all drivers support.

[Daniele Castagna, 2016/05/04 19:44:02]

Is it true that if the processor architecture is X86 we're always using i915
drivers?

If that is true on ChromeOS, then LGTM.

[dshwang, 2016/05/05 07:09:09]

Yes, All Intel architecture uses i915 in minigbm.

There is some naming confusion between i965 and i915. There are two user level
libraries; i965_dri.so and i915_dri.so However, in the kernel, there is only one
implementation, i915.ko
Unfortunately, i965_dri.so talks with i915.ko. This confusing naming causes many
misleading. i915 in minigbm deals with both i915 and i965.

FYI, since chromeos was introduced, all Intel architecture has used i965.

i915 in comment is a bit wrong, in the sense. I'll change it to "Intel driver".

+#endif
+            format == gfx::BufferFormat::BGRA_8888;
 #else
         return false;
 #endif