Update to Chromium revision a106f0ab (#464641)

- Remove CefWindowInfo.transparent_painting_enabled. Set
  CefBrowserSettings.background_color to an opaque or transparent
  value instead.

libcef/browser/views/browser_platform_delegate_views.h

@@ -42,6 +42,7 @@ class CefBrowserPlatformDelegateViews :
   void PopupBrowserCreated(
       CefBrowserHostImpl* new_browser,
       bool is_devtools) override;
+  SkColor GetBackgroundColor() const override;
   void WasResized() override;
   void SendKeyEvent(const content::NativeWebKeyboardEvent& event) override;
   void SendMouseEvent(const blink::WebMouseEvent& event) override;