Ensure that hardware Bitmap has a ColorSpace

Bug: 129355537
Test: I9e004fbb7c966bb58ae374087fecd66a1bb72346

android_view_ThreadedRenderer_createHardwareBitmapFromRenderNode in
SkiaGL could create an android::Bitmap without an SkColorSpace. Treat
HAL_DATASPACE_UNKNOWN as sRGB, as this is how we treat it internally.

Change-Id: Iad7f7d7cafce0a8759a84a4296ae5c3ce86dff4c