AutoFill: Release the cached frame when we receive the frameDestroyed() message
from WebKit.

BUG=48857
TEST=none

Review URL: http://codereview.chromium.org/3173005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55789 0039d316-1c4b-4281-b951-d872f2087c98
void RenderView::EnsureDocumentTag() {
#if defined(OS_MACOSX)
  if (!has_document_tag_) {
    Send(new ViewHostMsg_GetDocumentTag(routing_id_, &document_tag_));
    has_document_tag_ = true;
  }
#endif
}

void RenderView::EnsureDocumentTag() {
#if defined(OS_MACOSX)
  if (!has_document_tag_) {
    Send(new ViewHostMsg_GetDocumentTag(routing_id_, &document_tag_));
    has_document_tag_ = true;
  }
#endif
}
