Bug 971942: 1. layers.async-video.enabled moved to gfxPrefs and only evaluated at startup. r=nsilva
Bug 971942: 2. layout.frame_rate, layers.offmainthreadcomposition.frame-rate, layers.orientation.sync.timeout moved to gfxPrefs. The layers.offmainthreadcomposition.frame-rate is also changed to be a live preference so it does not need a restart. r=bgirard
Bug 971942: 3. layers.bufferrotation.enabled, layers.componentalpha.enabled, layers.scroll-graph, layers.acceleration.disabled, layers.acceleration.force-enabled moved to gfxPrefs. r=clord
Bug 971942: 4. layers.frame-counter, layers.draw-borders, layers.draw-tile-borders, layers.draw-bigimage-borders, layers.dump, layers.frame-counter, layers.progressive-paint, layers.low-precision-buffer moved to gfxPrefs. r=nsilva
Bug 971942: 5. nglayout.debug.widget_update_flashing, canvas.azure.accelerated, layers.offmainthreadcomposition.enabled, layers.offmainthreadcomposition.testing.enabled, layers.offmainthreadcomposition.force-enabled, layers.acceleration.disabled moved to gfxPrefs.  r=bschouten
Bug 971942: 6. layers.low-precision-resolution, layers.prefer-opengl, layers.prefer-d3d9, layers.enable-tiles, gfx.direct2d.disabled, gfx.direct2d.force-enabled, moved to gfxPrefs. r=bschouten
Bug 971942: 7. gfx.canvas.skiagl.dynamic-cache, gfx.canvas.skiagl.cache-items, gfx.canvas.skiagl.cache-size moved to gfxPrefs. r=jwillcox