[share] Show the share text in the iOS share preview panel

[mduong]

From flutter#2825

Description

Show the share text in the iOS share preview panel.

Before it just didn't show any preview of the text being shared.

Related Issues

N/A.

Checklist

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
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Breaking Change

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• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
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[nanda-prbot]

@mduong needs to request domain review.
@mduong needs to request platform review, or explicitly opt out, e.g.:

/no-platform

_{HOW TO: Request Reviewers}

[mduong]

/domain @mseijas @amyslies
/platform @mseijas @samandmoore

[nanda-prbot]

Needs somebody from @mseijas and @amyslies to claim domain review
Needs somebody from @mseijas and @samandmoore to claim platform review

Use the shovel operator to claim, e.g.:

@myname << domain && platform

_{HOW TO: Claim a Review}

[mduong]

Matt ran into this issue when testing:

Here it is with this fix:

[mseijas]

<< domainLGTM
<< platformLGTM

[nanda-prbot]

Approved! 💅 🎁 💫