Don't change Document load progress in any page dismissal events.

This can confuse the logic for blocking modal dialogs.

BUG=536652

Review URL: https://codereview.chromium.org/1373113002

Cr-Commit-Position: refs/heads/master@{#351419}
void Document::writeln(const String& text, Document* ownerDocument, ExceptionState& exceptionState)
{
    write(text, ownerDocument, exceptionState);
    if (exceptionState.hadException())
        return;
    write("\n", ownerDocument);
}

void Document::writeln(const String& text, Document* ownerDocument, ExceptionState& exceptionState)
{
    write(text, ownerDocument, exceptionState);
    if (exceptionState.hadException())
        return;
    write("\n", ownerDocument);
}
