Handle GL_READ_BUFFER being GL_NONE in getReadAttachment()
Handle GL_READ_BUFFER being GL_NONE in getReadAttachment()

Change-Id: If3883de8f49a3fb33ecc598ba0b86c658cd3f0ca
Reviewed-on: https://chromium-review.googlesource.com/415565
Reviewed-by: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Commit-Queue: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

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