Expected Result: The hit region for the second region association is removed. Canvas mouse events in canvas have no id resulting from a hit from the second region. Each hit region must be exposed as a best fit rectangle in screen coordinates in the platform accessibility API implementation for the corresponding fallback elements from the first two associations. (Note: clearing the hit region has no effect on the location of the fallback elements. It is up to the author to either remove the fallback elements or assign new locations to them via hit regions or drawFocusIfNeeded().
Test file: The test file should initially set up a hit region for each fallback element using addHitRegion with an associated id and the corresponding fallback element represented by the control at load time and then call clearHitRegions(). The test file should print out mouse events associated with the ids in an area outside the canvas element. An accessibility test tool must be used so that the tester can validate that the region associated with the control matches the screen location of the hit region as a best fit rectangle.