Update video overlay to use BGRA_8888 format

This format is better supported and is the default format used for
scanout buffer allocation.

Bug: b/74993970
Test: Ran on device and ensured buffer allocation doesn't fail.
Change-Id: I8743c9166e6ad41588418d10059fe2bac34fce35
Reviewed-on: https://chromium-review.googlesource.com/964893Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Sergey Volk <servolk@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543758}

media/renderers/video_overlay_factory.cc

@@ -25,11 +25,11 @@ class VideoOverlayFactory::Texture {
     if (!gl)
       return;
     gpu_memory_buffer_ = gpu_factories_->CreateGpuMemoryBuffer(
-        gfx::Size(1, 1), gfx::BufferFormat::RGBA_8888,
+        gfx::Size(1, 1), gfx::BufferFormat::BGRA_8888,
         gfx::BufferUsage::SCANOUT);
     if (gpu_memory_buffer_) {
       image_id_ = gl->CreateImageCHROMIUM(gpu_memory_buffer_->AsClientBuffer(),
-                                          1, 1, GL_RGBA);
+                                          1, 1, GL_BGRA_EXT);
       }
       if (image_id_) {
         gl->GenTextures(1, &texture_id_);