[Android WebView] Only send extra headers for the main page

Unlike Chromium, WebViewClassic has a very narrow set of conditions
when extra headers set for a navigation are actually added to requests.

To fix that, instead of passing the extra headers from AwContents.loadUrl
down to NavigationController, we stash them into our ResourceContext
and inject from AwResourceDispatcherHostDelegate when needed.

The resulting behavior seems to be compatible with WebViewClassic,
except that we also inject headers for back / forward navigations, as this
seems to be more consistent with the legacy behavior of injecting them
on page reload.

BUG=306873

Review URL: https://codereview.chromium.org/99683006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239807 0039d316-1c4b-4281-b951-d872f2087c98
Fix Java style issues in base/

BUG=320711
NOTRY=true

Review URL: https://codereview.chromium.org/104653013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239808 0039d316-1c4b-4281-b951-d872f2087c98
Increase maximum value for Ash.TouchDuration

BUG=327341

Review URL: https://codereview.chromium.org/105003003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@239809 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 239808
SVN changes up to revision 239809