Add a `getDataIfSmallerThan()` API to `nsIClipboard`. This API allows data to be retrieved only if the size of clipboard's contents is smaller than the specified threshold. The parameters are `aTransferable`, `aWhichClipboard` and `aRequestingWindowContext`, similar to [nsIClipboard.getData()](https://searchfox.org/firefox-main/rev/7709f0a26aeb3c39a5fd86e794425530f0d0b528/widget/nsIClipboard.idl#165-181). In addition, it takes `aThreshold`, which defines the threshold value. (Currently, it only targets plain/text content and checks its character count.)
The reason I want to add this is for use in the urlbar and places modules.
For example, we currently want to change the context menu items based on the clipboard's content. However, when the content is very large, it takes a significant amount of time to retrieve and parse it. [1]
Additionally, while there is a feature to suggest URLs when the clipboard contains a URL[2], we cannot enable this feature by default due to the same reason.
To resolve them, adds the above API, we want to make very large content ignorable.
[1] https://bugzilla.mozilla.org/show_bug.cgi?id=1874203
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=1842230
Differential Revision: https://phabricator.services.mozilla.com/D280552
Daisuke Akatsuka
31e276101e