It could theoretically, but OpenSim compatible viewers (such as Firestorm) have a codebase that is far from optimized and the WebGL code that would result from the compilation would not likely provide good browser-rendered performance. To make that a viable option you’d likely need to switch the viewer code to use WebMetal instead of OpenGL and that is not a project that the OpenSim community can realistically do in any meaningful time frame.
I actually promoted going this WebGL-based route years ago when there were more people involved in OpenSim development, but the OpenSim community didn’t want to pitch into the effort:
In any case, I think this is a realistic option for High Fidelity which has capable graphics developers on hand to make the change. They could then have a single codebase for High Fidelity that would run anywhere where Chrome runs (using WebVR for VR mode).