**You need to accept camera permission to use using below lines in your activity.**
webview.setWebChromeClient(new WebChromeClient() { @Override public void onPermissionRequest(final PermissionRequest request) { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { request.grant(request.getResources()); } } });

I was trying same thing. Below code worked to me.
First in manifest file we have to add camera hardware permission true using uses permission tag.
Then need to accept camera permission to use using below lines in your activity.
webview.setWebChromeClient(new WebChromeClient() {
@Override public void onPermissionRequest(final PermissionRequest request) { if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { request.grant(request.getResources()); } }
});