- Allow asynchronous continuation of OnBeforeResourceLoad (issue #1593).

- Use CefRequestCallback for most asynchronous CefRequestHandler methods.

include/internal/cef_types.h

@@ -651,6 +651,26 @@ typedef struct _cef_browser_settings_t {
   cef_string_t accept_language_list;
 } cef_browser_settings_t;
 
+///
+// Return value types.
+///
+typedef enum {
+  ///
+  // Cancel immediately.
+  ///
+  RV_CANCEL = 0,
+
+  ///
+  // Continue immediately.
+  ///
+  RV_CONTINUE,
+
+  ///
+  // Continue asynchronously (usually via a callback).
+  ///
+  RV_CONTINUE_ASYNC,
+} cef_return_value_t;
+
 ///
 // URL component parts.
 ///