If JavaScript shows a dialog, cause the page to lose fullscreen.

BUG=670135, 550017, 726761, 728276

Review-Url: https://codereview.chromium.org/2906133004
Cr-Commit-Position: refs/heads/master@{#478884}
  LoadingStateChangedDelegate()
      : loadingStateChangedCount_(0)
      , loadingStateToDifferentDocumentCount_(0) {
  }

  LoadingStateChangedDelegate()
      : loadingStateChangedCount_(0)
      , loadingStateToDifferentDocumentCount_(0) {
  }
