Plumb the value of the "capture" attribute through the framework
down to the embedder.
Requires a change in WebKit
(I0a921be31fda79a43c05da4fe22d9c808d92709c)
and Browser (I38dfe2df043fdba1388384dbd3b5370737eb38e5).
Bug: 5771207
Change-Id: I494adc1274ca21ce8fe52a6c7b6b758217927e66