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::OnGetAccessibilityTree() {
  if (accessibility_.get())
    accessibility_->clear();
    accessibility_.reset(WebAccessibilityCache::create());
    accessibility_->initialize(webview());

  WebAccessibilityObject src_tree = webview()->accessibilityObject();
  webkit_glue::WebAccessibility dst_tree(src_tree, accessibility_.get());
  Send(new ViewHostMsg_AccessibilityTree(routing_id_, dst_tree));
}

void RenderView::OnGetAccessibilityTree() {
  if (accessibility_.get())
    accessibility_->clear();
    accessibility_.reset(WebAccessibilityCache::create());
    accessibility_->initialize(webview());

  WebAccessibilityObject src_tree = webview()->accessibilityObject();
  webkit_glue::WebAccessibility dst_tree(src_tree, accessibility_.get());
  Send(new ViewHostMsg_AccessibilityTree(routing_id_, dst_tree));
}
