If you want to send an email via the Gmail iOS app containing the URL and title of a web page, you can't simply use the Share button. But you can use a bookmarklet, as posted by Federico Viticci on MacStories. Save the following bookmarklet in your browser:
javascript:window.location='googlegmail:///co?subject='+encodeURIComponent(document.title)+'&body='+encodeURIComponent(location.href);
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