cc: Update TestContextProvider to use SkNullGLContext.
cc: Update TestContextProvider to use SkNullGLContext.

Currently TCP uses GrGLCreateNullInterface() to create a null interface.
This has limitations as multiple NullInterfaces on a single thread share
the same state, and the state can't be re-bound to different threads.

Updating to use SkNullGLContext which addresses the threading issues
and behaves like GrContextForWebGraphicsContext3D() in terms of binding.
This is required for test support for threaded GPU rasterization.

BUG=454500

Review URL: https://codereview.chromium.org/924603002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#316075}

TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,ltilve/chromium,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,fujunwei/chromium-crosswalk,chuan9/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,ltilve/chromium,ltilve/chromium,Just-D/chromium-1,fujunwei/chromium-crosswalk,Just-D/chromium-1,Chilledheart/chromium,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,ltilve/chromium,Chilledheart/chromium,chuan9/chromium-crosswalk,Just-D/chromium-1,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,Chilledheart/chromium,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,fujunwei/chromium-crosswalk,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,ltilve/chromium,hgl888/chromium-crosswalk,Pluto-tv/chromium-crosswalk,ltilve/chromium,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,hgl888/chromium-crosswalk,ltilve/chromium,Chilledheart/chromium,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,axinging/chromium-crosswalk,Chilledheart/chromium,fujunwei/chromium-crosswalk,ltilve/chromium,chuan9/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,fujunwei/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,ltilve/chromium,Just-D/chromium-1,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk