Improve GL shader YUV adjustment.

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 5cbfd39699849c861b82da01a7221b90133f09c5..3f943723c3785cd20dd073226b4aba27143841c8 100644
--- a/cc/resources/video_resource_updater.cc
+++ b/cc/resources/video_resource_updater.cc
@@ -152,7 +152,8 @@ VideoFrameExternalResources::VideoFrameExternalResources()
     : type(NONE),
       read_lock_fences_enabled(false),
       offset(0.0f),
-      multiplier(1.0f) {}
+      multiplier(1.0f),
+      bits_per_channel(8) {}
 
 VideoFrameExternalResources::VideoFrameExternalResources(
     const VideoFrameExternalResources& other) = default;
@@ -375,6 +376,8 @@ VideoFrameExternalResources VideoResourceUpdater::CreateForSoftwarePlanes(
 
   VideoFrameExternalResources external_resources;
 
+  external_resources.bits_per_channel = bits_per_channel;
+
   if (software_compositor) {
     DCHECK_EQ(plane_resources.size(), 1u);
     PlaneResource& plane_resource = *plane_resources[0];