The Chrome history page which you can visit by going to chrome://history (or by pressing Ctrl+H or through History sub menu) has got Ctrl+A support for multiple items selection.
Chrome history Page: Ctrl+A now selects all items
Till now to check and delete all history items in Chrome history page after doing a search, you need to first select an entry, then Shift+Click to select last entry. Now the addition of Ctrl+A support to the history page makes it easy to select or unselect multiple history items.
Also READ: Google Chrome to offer group visits by domain option for its history Page
The thing is, only 150 visible items are selected if the page has more history items.
If you want to delete all Chrome browsing history, its better to use clear browsing data dialog and that makes sense. The bug – Ctrl+a should select all entries on chrome://history has been marked as fixed and working in Chrome 66 dev.
You may want to read the following articles related to Chrome history.
Clearing Specific Website’s Browsing history from Google Chrome
History Limiter allows Google Chrome to Keep History for Specified number of days
HistoryStats for Chrome Provides Statistical And Graphical Display of browser’s History