ozone: support gfx::BufferFormat::RGBX_8888 as a native pixmap format.

ui/ozone/platform/drm/gpu/gbm_buffer_base.cc

Index: ui/ozone/platform/drm/gpu/gbm_buffer_base.cc
diff --git a/ui/ozone/platform/drm/gpu/gbm_buffer_base.cc b/ui/ozone/platform/drm/gpu/gbm_buffer_base.cc
index 5f27c51e7e9f04c1625622f7384e6f4765448932..4da64389d10836c5452b61591986c3f0b7fcd554 100644
--- a/ui/ozone/platform/drm/gpu/gbm_buffer_base.cc
+++ b/ui/ozone/platform/drm/gpu/gbm_buffer_base.cc
@@ -15,15 +15,8 @@ GbmBufferBase::GbmBufferBase(const scoped_refptr<DrmDevice>& drm,
                              gbm_bo* bo,
                              bool scanout)
     : drm_(drm), bo_(bo) {
+  fb_pixel_format_ = gbm_bo_get_format(bo);

[dshwang, 2015/11/27 17:59:54]

fb_pixel_format_ is used in GetBufferFormat() even for GPU_READ_WRITE buffer.

[reveman, 2015/11/27 20:09:33]

can you move this into the initialization list? 

[kalyank, 2015/11/27 21:15:20]

Here storage format can be different to pixel format. This is not something
OverlayCandidateHost can decide as it’s very specific to how we register the
framebuffer. Currently, we always create fb of 24 bitcolordepth.
GetFramebufferPixelFormat returns the Frame buffer format for this buffer.
GetBufferFormat should return the pixel format, we could just query it directly
from gbm there? If we want to cache the value than we need to separate it from
fb_pixel_format_

   if (scanout) {
-    fb_pixel_format_ = gbm_bo_get_format(bo);
-    if (fb_pixel_format_ == GBM_FORMAT_ARGB8888)
-      fb_pixel_format_ = GBM_FORMAT_XRGB8888;

[dshwang, 2015/11/27 17:59:54]

This hack was introduced by https://codereview.chromium.org/1314553002
Choosing XRGB or XRGB is role of drm_overlay_candidates_hosts, not here.

It causes crash of gl_unittests in 
https://code.google.com/p/chromium/codesearch#chromium/src/ui/ozone/platform/...

-
-    // For now, we only support XRGB and UYVY format.
-    DCHECK(fb_pixel_format_ == GBM_FORMAT_XRGB8888 ||
-           fb_pixel_format_ == GBM_FORMAT_UYVY);
-
     uint32_t handles[4] = {0};
     handles[0] = gbm_bo_get_handle(bo).u32;
     uint32_t strides[4] = {0};