PDF files no more displayed correctly

I just upgraded from Moodle 1.7.1 to Moodle 1.8+ and noticed something wrong when displaying PDF files.

Only in the case "Keep page navigation visible on the same page" is selected, the PDF file is displayed as an embedded object! It means the PDF Adobe Reader plugin is no more used! As a consequence:

• the PDF byteserving ("fast web viewing / one page at a time") cannot work!
• the PDF window size is fixed, and is no more "adjusted" to the size of the browser window;
• ... and still more inconveniences.

As a work around, what can be done is:

• do not select "Keep page navigation visible on the same page" (but then you lose this functionality of course);
• adapting the .../type/file/resource.class.php file by removing "$embedded = true" when a PDF format has to be displayed.

What is making me really astonished is that it seems that this "bug" has been asked by somebody in ticket "MDL-9198 - Frameset used to display PDF" in order, if I well understand, to be compliant with XHTML rules.

This problem was not present in Moodle 1.7.1.