The MemPage.aDataEnd field should point to the end of the data buffer for

The MemPage.aDataEnd field should point to the end of the data buffer for
the page, not just the end of the usable portion of that buffer.  The purpose
aDataEnd is to detect cells that overflow the page, and that won't work on a
page with reserved bytes and a cell that starts in the reserved region, unless
the boundary is at the very end of the page. Chromium issue 1276294.

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