Guard against the same PrintWebViewHelper being re-entered.

BUG=159165

Review URL: https://chromiumcodereview.appspot.com/11367076

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@165821 0039d316-1c4b-4281-b951-d872f2087c98
void PrintWebViewHelper::PrintPreviewContext::InitWithNode(
    const WebKit::WebNode& web_node) {
  DCHECK(!web_node.isNull());
  DCHECK(web_node.document().frame());
  DCHECK(!IsRendering());
  state_ = INITIALIZED;
  frame_ = web_node.document().frame();
  node_ = web_node;
}

void PrintWebViewHelper::PrintPreviewContext::InitWithNode(
    const WebKit::WebNode& web_node) {
  DCHECK(!web_node.isNull());
  DCHECK(web_node.document().frame());
  DCHECK(!IsRendering());
  state_ = INITIALIZED;
  frame_ = web_node.document().frame();
  node_ = web_node;
}
