Combine AsyncChannel, SyncChannel, and RPCChannel into one class (bug 901789, r=cjones,bent).

--HG--
rename : ipc/glue/RPCChannel.cpp => ipc/glue/MessageChannel.cpp
rename : ipc/glue/RPCChannel.h => ipc/glue/MessageChannel.h
Bug 920055 - Honor install-strip and STRIP_FLAGS when packaging tests. r=ted

--HG--
extra : rebase_source : 6845c548309113cecdf30d6ca3a885b39b0c0d03
Bug 921440 - Build ASan optimized builds with -gline-tables-only. r=ted

--HG--
extra : rebase_source : 748468aacb041aef4769c41deb5e7864645a3a24
Bug 911346 - Add a test for WebGL context creation. - r=bjacob