Bug 803299 - Enable 32-bit colour on Android. r=kats
Bug 803299 - Respect gfx.android.rgb16.force pref. r=blassey
Bug 803299 - More tests pass on Android with 24-bit colour. r=blassey

Tests that were marked as failing now pass with increased colour depth.
Bug 803299 - JPEG srgb icc fails on Android in 24-bit colour. r=jrmuizel
Bug 803299 - Some tests require extra fuzzing on Android in 24-bit colour. r=blassey
Bug 803299 - Replace black.png with black.html for webgl-color-alpha-test. r=jrmuizel

webgl-color-alpha-test fails to render the image correctly since switching on
24-bit rendering, presumably due to async image decoding. Instead, just replace
the pure black 256^2 image with a page that renders the same using a div.
Bug 803299 - Some SVG tests need more fuzzing on Android with 24bpp. r=jwatt