better scrolling in JS-less single-message conversation view

Allow simultaneous horizontal and vertical scrolling when the WebView is
embedded in a ScrollView by supplementally sending touch events to the
ScrollView when it normally wants to intercept AND the WebView handled
the touch. Touch interception happens as normal on any other child.

Bug: 8368615
Change-Id: I21f8721c673fd8146992b933d0c966d59c376795
4 files changed