Stack preview back at top after an active contents switch.

BUG=161233

Review URL: https://codereview.chromium.org/11428083

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@170973 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/frame/browser_view.cc

@@ -1661,15 +1661,7 @@ void BrowserView::ActiveTabChanged(content::WebContents* old_contents,
 
   if (change_tab_contents) {
     contents_container_->SetWebContents(new_contents);
-#if defined(USE_AURA)
-    // Put the Instant preview back on top in case it is showing custom new tab
-    // page content.
-    if (contents_->preview_web_contents()) {
-      ui::Layer* preview_layer =
-          contents_->preview_web_contents()->GetNativeView()->layer();
-      preview_layer->parent()->StackAtTop(preview_layer);
-    }
-#endif
+    contents_->MaybeStackPreviewAtTop();
   }
 
   if (!browser_->tab_strip_model()->closing_all() && GetWidget()->IsActive() &&

chrome/browser/ui/views/frame/contents_container.cc

@@ -54,6 +54,14 @@ void ContentsContainer::SetPreview(views::WebView* preview,
   Layout();
 }
 
+void ContentsContainer::MaybeStackPreviewAtTop() {
+  if (preview_) {
+    RemoveChildView(preview_);
+    AddChildView(preview_);
+    Layout();
+  }
+}
+
 void ContentsContainer::SetActiveTopMargin(int margin) {
   if (active_top_margin_ == margin)
     return;

chrome/browser/ui/views/frame/contents_container.h

@@ -45,6 +45,10 @@ class ContentsContainer : public views::View {
                   int height,
                   InstantSizeUnits units);
 
+  // When the active content is reset and we have a visible preview,
+  // the preview must be stacked back at top.
+  void MaybeStackPreviewAtTop();
+
   content::WebContents* preview_web_contents() const {
     return preview_web_contents_;
   }