>>> My Info: Win7_64, Nightly 49, 32bit, ID 20160526082509 STR_1: (normal fullscreen) 1. Switch to fullscreen mode (F11) 2. Hover mouse over Australis menu button 3. Open Findbar, focus Findbar (F3) 4. Press Escape once AR: Toolbars hide ER: Toolbars should stay visible STR_2: (DOM fullscreen) 1. Open https://www.youtube.com/watch?v=mD3v1B_aXw0 or attachment 8666690 [details] in that window 2. Click fullscreen button to switch to DOM fullscreen 3. Open Findbar, focus Findbar (F3) 4. Press Escape once AR: Browser exits DOM fullscreen, and findbar stays open, but it's not focused anymore ER: Either X or Y (only 1 action at the same time) X) Browser shouls hide findbar and do not leave DOM fullscreen Y) OK, browser should leave DOM fullscreen and do not hide findbar, but findbar should be focused STR_3: (DOM fullscreen) 1. Open https://www.youtube.com/watch?v=mD3v1B_aXw0 or attachment 8666690 [details] in that window 2. Click fullscreen button to switch to DOM fullscreen 3. Open devtools -> inspector, click in markup 4. Press Escape once AR: Split console opens AND browser exits DOM fullscreen (2 actions at the same time) ER: Either X or Y (only one action) X) Split console should toggle, and browser should stay in DOM fullscreen Y) Split console should NOT toggle, and browser should exit DOM fullscreen STR_4: (reference of good behavior) 1. Switch to fullscreen mode (F11) 2. Hover mouse over Australis menu button 3. Open bookmarks sidebar and focus filter field (Ctrl+B). Type "a" 4. Press Escape once AR: Filter in bookmarks sidebar becomes empty, and browser still displays toolbars, just as expected.

Is this related to bug 1327562?

No. In that bug browser shows tabs toolbar + navigation toolbar if mouse pointer is placed on topmost pixel, in some cases.