You can create a new V8 Context via its API and use that to execute your JavaScript, look into https://android.googlesource.com/platform/external/v8 include directory which contains two C++ header files. Link against the libwebcore.so (compiled from https://android.googlesource.com/platform/external/webkit) library via the NDK, nothing special.
v8::Persistent<v8::Context> context = v8::Persistent<v8::Context>::New(v8::Context::New());
context->Enter();
Refer to https://developers.google.com/v8/get_started which will work on Android. Just make sure the device actually ships with V8 (some older devices ship with JSC [JavaScript Core]).