Fix a typo that caused child views to stay visible after hide.

R=ekaramad@chromium.org,lfg@chromium.org
BUG=628704

Change-Id: I88b95a335e8f97ef5076329a49b52d482fe297f4
Reviewed-on: https://chromium-review.googlesource.com/690348Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Bo <boliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505228}

content/browser/web_contents/web_contents_impl.cc

@@ -1532,7 +1532,7 @@ void WebContentsImpl::WasHidden() {
       view->Hide();
 
     if (!ShowingInterstitialPage())
-      SetVisibilityForChildViews(true);
+      SetVisibilityForChildViews(false);
 
     SendPageMessage(new PageMsg_WasHidden(MSG_ROUTING_NONE));
   }