[lookandfeel] Avoid rendering invisible contents
An opacity of 0 but still visible still results in nodes in the scenegraph, which is wasteful. This is shown in gammaray with some warnings. Enabled is also bound to visible as if a text field has focus it still animates the cursor icon even if inivisble, producing wakeups. BUG: 347772 FIXED-IN: 5.21
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c0415515