Add support for converting I420 software frames into NV12 hardware frames

cc/resources/video_resource_updater.cc

Index: cc/resources/video_resource_updater.cc
diff --git a/cc/resources/video_resource_updater.cc b/cc/resources/video_resource_updater.cc
index 5911d347597a3800dc5e10d4ffe0c97019dff53b..5b6fc9a4d37ad0009998e3a69d92303a6067a71b 100644
--- a/cc/resources/video_resource_updater.cc
+++ b/cc/resources/video_resource_updater.cc
@@ -407,6 +407,10 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForHardwarePlanes(
       external_resources.type = VideoFrameExternalResources::YUV_RESOURCE;
       break;
     case media::PIXEL_FORMAT_NV12:
+      DCHECK(video_frame->mailbox_holder(0).texture_target ==
+             GL_TEXTURE_RECTANGLE_ARB);
+      external_resources.type = VideoFrameExternalResources::IO_SURFACE;
+      break;
     case media::PIXEL_FORMAT_YV12:
     case media::PIXEL_FORMAT_YV16:
     case media::PIXEL_FORMAT_YV24:
@@ -420,6 +424,8 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForHardwarePlanes(
 
   for (size_t i = 0; i < textures; ++i) {
     const gpu::MailboxHolder& mailbox_holder = video_frame->mailbox_holder(i);
+    if (mailbox_holder.mailbox.IsZero())

[Daniele Castagna, 2015/08/25 15:08:42]

This is because |textures| == 2 while we created only one texture, right?

We tried to add a VideoFrame::TextureFormat and VideoFrame::NumTextures, but it
was removed.

It's pretty confusing to see int textures = NumPlanes(format), and then this to
correct the number of textures. :/

[Andre, 2015/08/25 18:19:57]

Yes, let me see if I can find a better way to do this.

+      break;
     external_resources.mailboxes.push_back(
         TextureMailbox(mailbox_holder.mailbox, mailbox_holder.texture_target,
                        mailbox_holder.sync_point, video_frame->coded_size(),