Revert 212329 "Reland "Close web contents modal dialogs on conte..."

Revert 212329 "Reland "Close web contents modal dialogs on conte..."

Causes several problems related to the print preview dialog:
  http://crbug.com/262023
  http://crbug.com/262916
  http://crbug.com/265427

> Reland "Close web contents modal dialogs on content load start"
>
> Address the failure of some web contents modal dialogs to close when
> interstitial WebUI is displayed by closing the dialogs on content load start.
> Remove existing ad hoc support in dialogs for closing on page loading in favor
> of a uniform approach.
>
> I'm using load start as the trigger for dialog close as this seems to be the
> point in time at which the user first perceives the page to be changing.
>
> Notes on the print preview changes: with this change the dialog is closed when
> load starts and the initiator tab gets removed via RemovePreviewDialog, so there
> is no longer a need to handle NOTIFICATION_NAV_ENTRY_COMITTED for the initiator
> tab.  The PrintViewManager::PrintPreviewDone() DCHECK is removed since now
> PrintViewManager::RenderViewGone() may be invoked and print_preview_state_ reset
> due to WebContents closure before the dialog is destroyed and PrintPreviewDone()
> is invoked.
>
> BUG=240575
>
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=211058
>
> Review URL: https://chromiumcodereview.appspot.com/17500003

TBR=wittman@chromium.org

Review URL: https://codereview.chromium.org/21372006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214775 0039d316-1c4b-4281-b951-d872f2087c98