The encoder color info [defaults](https://cs.android.com/android/platform/superproject/+/master:frameworks/av/media/libstagefright/foundation/ColorUtils.cpp;l=377;drc=891c19ccfa4953b5e5f7b87118e007b994d8074c) to a value that depends on the input resolution, but when tone-mapping is enabled we should always get BT.709 color space. Hard-code this constant for now to avoid behavior depending on the resolution. A future change should use the decoder output media format to populate the color info. PiperOrigin-RevId: 465070378
