Document WebView Metrics opt out API
Document WebView Metrics opt out API

BUG:22665268
Change-Id: Ib2f7b2a340e27d7d3faf5bfbf6c2216d3c1549e4

xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base,xorware/android_frameworks_base