Fix non-virtual destructor in DelegatedFrameHostClient

Review-Url: https://codereview.chromium.org/2593603002
Cr-Commit-Position: refs/heads/master@{#439791}

content/browser/renderer_host/delegated_frame_host.h

@@ -53,6 +53,8 @@ class ResizeLock;
 // display them.
 class CONTENT_EXPORT DelegatedFrameHostClient {
  public:
+  virtual ~DelegatedFrameHostClient() {}
+
   virtual ui::Layer* DelegatedFrameHostGetLayer() const = 0;
   virtual bool DelegatedFrameHostIsVisible() const = 0;
 

content/browser/renderer_host/delegated_frame_host_client_aura.h

@@ -19,7 +19,7 @@ class CONTENT_EXPORT DelegatedFrameHostClientAura
  public:
   explicit DelegatedFrameHostClientAura(
       RenderWidgetHostViewAura* render_widget_host_view);
-  virtual ~DelegatedFrameHostClientAura();
+  ~DelegatedFrameHostClientAura() override;
 
  protected:
   RenderWidgetHostViewAura* render_widget_host_view() {