Add an API on the Java side to allow WebKit to pause the current load. This is...

Add an API on the Java side to allow WebKit to pause the current load. This is used when the plugin is streaming data but it's
buffer is full. In that case, WebCore instructs the laoder to pause loading to give the plugin a chance to clear it's buffer and
continue.

Requires an external/webkit change.

Change-Id: Iec96a6325d92e979cbdc53289c2a20cad940ded2