Add support for HTML Media Capture "capture" attribute.

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
3 files changed