I discovered today that Chrome was occasionally turning on the dGPU of my 15" rmbp with 750M, which affects battery life negatively. I was able to isolate the issue to webgl. If the site activates webgl (example, google maps), then the dgpu activates. WebGL can be disabled in chrome://flags, and it doesn't seem to cause any changes in web sites whatsoever. When webgl is disabled in chrome, the dGPU never activates in my testing.