Strange zoom behavior when image is larger than the window

[David-Hari]

Environment: Windows 7, Firefox 31 and Pale Moon 24, no other add-ons

Description: Mouse cursor shows the zoom icon (magnifying glass with plus or minus in it). Left clicking sometimes toggles zoom levels, but it seems to interfere with the standard zoom behaviour of Image Tweak.

Add-on Options:

Reproduction steps:

1. View an image whose dimensions exceed that of the browser window (i.e. at default zoom level, it wouldn't fit in view). Note that the image fits the entire window (as per the options) and that the title (in Pale Moon or older Firefox) includes the percent that it has been scaled by (e.g. 64%)
2. Left click on the image. Note that the zoom level does not change, but the title now says "Scaled" followed by the percentage. Also, the mouse cursor changes from minus to plus
3. Continuing to left click just toggles the title and cursor.
4. Use the mouse wheel to zoom in. Note the percent in the title changes (e.g. to 110%)
5. Left click. Note that the zoom level still does not change. However, the title now shows the original scale percent (e.g. 64%)
6. Click again. Note that the title does not include a percent. The image still does not change zoom level, but appears to just shift position.
7. Continuing to click just cycles these states. If you click quick enough, it seems to register as a double-click, and zoom in (as per the behaviour of Image Tweak). However, it also handles that as two single clicks.