Fix AutofillDialogViews minimum/preferred size and resize issues.

Return unclamped preferred sizes and accurate minimum sizes.
Call UpdateWebContentsModalDialogPosition on content size changes.
(this clamps the dialog size and and places it in the correct bounds)

Add AutofillDialogSignInDelegate::UpdateLimitsAndEnableAutoResize().
Return more accurate minimum and maximum sign-in web contents sizes.
(updates the sign-in web contents' auto-resize limits on browser resizes)

Fix empty |notification_area_| sizing/padding logic (ignore insets).
Fix AutofillDialogCocoa override ordering (to match the base class).

BUG=284797
TEST=Autofill dialog (showing form or sign-in webview) resizes nicely with the host browser window on Win, Linux Aura, and ChromeOS. No behavior changes on Mac.
R=estade@chromium.org,groby@chromium.org

Review URL: https://codereview.chromium.org/25666002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227867 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227867