Refactor MuteToggle#update

[kevinlitchfield]

Since MuteToggle#update performs two distinct tasks, I thought it might be worth doing a small refactoring, if the maintainers are in agreement.

Summary of proposed changes:

• Extract updateIcon_ and updateControlText_ private methods.
• Expand original comment for update and comment updateIcon_ and updateControlText_.
• Rename toMute to text. toMute sounds to me like a Boolean, but its role is to store the correct current text for controlText.
• Add missing JSDoc directive to update.

Question

I'm unsure of the meaning of the following comment on the section of code that I've put in updateControlText_:

  // This causes unnecessary and confusing information for screen reader users.

Does this mean:

1. There is an existing problem with this code for users of screen readers?
2. There is not a problem, but there would be a problem if MuteToggle.controlText were updated each time volume was updated?

I've left that part out for now pending an answer.

[gkatsev]

This looks great, thanks @kevinlitchfield.

I think the punctuation of that comment is misleading. I believe it means that the check is necessary so that the label won't get changed if there's no need to change it. If the label gets changes each time (even if to the same text), the screen reader would read it out and could cause confusion. So, #.2 is the correct meaning, I believe.

[brandonocasey]

@kevinlitchfield This needs a rebase on master when you get a chance

[kevinlitchfield]

@brandonocasey 👍