Add support for HTML Media Capture "capture" attribute.

Receive the value for the new "capture" attribute on HTML
file pickers, and do the right thing with it.

Requires changes in WebKit
(I0a921be31fda79a43c05da4fe22d9c808d92709c)

and the framework (I494adc1274ca21ce8fe52a6c7b6b758217927e66).

Bug: 5771207

Change-Id: I38dfe2df043fdba1388384dbd3b5370737eb38e5
6 files changed