Update to Chromium version 70.0.3538.0 (#587811)

Known issues:
- The CefLoadCRLSetsFile function needs to be re-implemented (see issue #2497).
- Linux: GTK2 support has been removed. The cefclient sample needs to be updated
  to use GTK3 (see issue #2014).

libcef/browser/extensions/extension_host_delegate.h

@@ -35,6 +35,10 @@ class CefExtensionHostDelegate : public ExtensionHostDelegate {
                                   content::MediaStreamType type,
                                   const Extension* extension) override;
   ExtensionHostQueue* GetExtensionHostQueue() const override;
+  gfx::Size EnterPictureInPicture(content::WebContents* web_contents,
+                                  const viz::SurfaceId& surface_id,
+                                  const gfx::Size& natural_size) override;
+  void ExitPictureInPicture() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(CefExtensionHostDelegate);