exo: Disable HW overlays for NV12

Starting from M68, we noticed some issues scanning out NV12 buffers
coming from exo.
This CL disables promoting exo NV12 buffers to HW overlays while we
investigate the issue further.

Bug: b/113362843
Change-Id: I8b3c5f7a5c8cc65a713f4791f461ebb760291c54
Reviewed-on: https://chromium-review.googlesource.com/1200944Reviewed-by: Hirokazu Honda <hiroh@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#588311}

components/exo/display.cc

@@ -107,7 +107,9 @@ std::unique_ptr<Buffer> Display::CreateLinuxDMABufBuffer(
   // Using zero-copy for optimal performance.
   bool use_zero_copy = true;
 
-  bool is_overlay_candidate = true;
+  // TODO(dcastagna): Re-enable NV12 format as HW overlay once b/113362843
+  // is addressed.
+  bool is_overlay_candidate = format != gfx::BufferFormat::YUV_420_BIPLANAR;
 
   return std::make_unique<Buffer>(
       std::move(gpu_memory_buffer), GL_TEXTURE_EXTERNAL_OES,