Currently wallpaperPrivate.getLocalImageData sends the binary data directly, which may be less efficient (the size for an e.g. 640x480 JPEG file can range from 35kb to 70kb).

We can create a file backed blob, and pass the uuid of the blob to *_custom_bindings.js, which will in turn call |TakeBrowserProcessBlob| to take the ownership of the Blob.

An example can be found here https://cs.chromium.org/chromium/src/extensions/renderer/resources/printer_provider_custom_bindings.js?type=cs&q=printer_provider_cus&l=3