Teach RenderScriptRuntime about changed context representation.
The runtime discovers contexts through RenderScriptRuntime::Capture*()
methods. These methods see the low-level context representation.
However, the runtime calls APIs that require the high-level context
representation. Therefore, it needs to call yet another API to find
the high-level representation associated with a given low-level
Differential Revision: https://reviews.llvm.org/D32184