Move GetPrintHandler to CefClient (see issue #2196)

This new location is preferred because we now know the associated CefBrowser
for all CefPrintHandler callbacks.

include/cef_print_handler.h

@@ -133,7 +133,8 @@ class CefPrintHandler : public virtual CefBaseRefCounted {
   // CefBrowserHost::PrintToPDF().
   ///
   /*--cef()--*/
-  virtual CefSize GetPdfPaperSize(int device_units_per_inch) {
+  virtual CefSize GetPdfPaperSize(CefRefPtr<CefBrowser> browser,
+                                  int device_units_per_inch) {
     return CefSize();
   }
 };