Where is a "Sync project with gradle files" button in Android Studio 3?

Question

This button disappeared from a new 3.1 version of AS Toolbar. Before it showed as:

Now it's missing:

Answer 1

EDIT: They like to keep playing with the toolbar.

Since Android Studio 3.3, the icon has been updated and moved back across to the right:

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Original answer:

It hasn't disappeared. They have just moved it between the Save and Sync files button on the far left end of the toolbar.