Merge pull request #1223 from LarissaSmith/master

Fix image stuck to mouse when right-clicking and left-clicking simult…

src/mousetracker.js

@@ -2879,6 +2879,12 @@
                 }
             }
 
+            // A primary mouse button may have been released while the non-primary button was down
+            if (pointsList.contacts > 0 && pointsList.type === 'mouse') {
+                // Stop tracking the mouse; see https://github.com/openseadragon/openseadragon/pull/1223
+                pointsList.contacts--;
+                return true;
+            }
             return false;
         }