[Android WebView] Separate TargetDensityDPI processing from other settings

Currently turning off SupportTargetDensityDPI also turns off the code path
that processes LoadWithOverviewMode and UseWideViewport settings. This
change makes the processing independent.

BUG=288037

Review URL: https://chromiumcodereview.appspot.com/23537032

git-svn-id: svn://svn.chromium.org/blink/trunk@157538 bbb929c8-8fbe-4397-9dbb-9b2b20218538