PDF: Enable tooltips in Print Preview UI
PDF: Enable tooltips in Print Preview UI

Previously, print preview was unable to access the
chrome.resourcesPrivate API due to cross-origin iframe issues,
preventing tooltips from loading. Following https://crrev.com/367293,
these issues are now resolved and it is possible to access translated
strings in print preview.

BUG=568037

Review URL: https://codereview.chromium.org/1552423002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#368007}

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