Bug 933082 - Part 1: make LayerTransactionChild reference-counted - r=nical
Bug 933082 - Part 2: propagate the mIPCOpen flag, avoid crashing in DestroySharedSurface on a dead channel - r=nical
Bug 933082 - Part 3: let ShadowLayerForwarder hold a strong ref to its LayerTransactionChild - r=nical
Bug 933082 - Part 4: let ClientLayerManager hold a ShadowLayerForwarder instead of inheriting from ShadowLayerForwarder. Make ISurfaceAllocator refcounted. Make SharedSurface_Gralloc keep its mAllocator alive - r=nical