webkit-utils: Check if the media engine will show the resource

cog_handle_web_view_load_failed() checks if the error is WEBKIT_MEDIA_ERROR
or WEBKIT_MEDIA_ERROR_WILL_HANDLE_LOAD and relies on WebKit in these cases.

Similarly it does the same for the case of WPE API previous to 2.0 but using
WEBKIT_PLUGIN_ERROR and WEBKIT_PLUGIN_ERROR_WILL_HANDLE_LOAD.

This reverts commit c7bdb9c.

core/cog-webkit-utils.c

@@ -72,6 +72,16 @@ cog_handle_web_view_load_failed (WebKitWebView  *web_view,
                                  GError         *error,
                                  void           *userdata)
 {
+    // If the resource is going to be shown by a plug-in or a
+    // media engine (for the case of API WPE2) just return FALSE and
+    // let WebKit handle it.
+#if COG_USE_WPE2
+    if (g_error_matches(error, WEBKIT_MEDIA_ERROR, WEBKIT_MEDIA_ERROR_WILL_HANDLE_LOAD))
+#else
+    if (g_error_matches(error, WEBKIT_PLUGIN_ERROR, WEBKIT_PLUGIN_ERROR_WILL_HANDLE_LOAD))
+#endif
+        return FALSE;
+
     // Ignore cancellation errors as the active URI may be changing
     if (g_error_matches (error,
                          WEBKIT_NETWORK_ERROR,