BHV-10256: optimize event bubbling using cached bubble target
add comment on private property
remove duplicated variable declaration
remove commented code which was for reference
fix merge conflicts while updating the original changes into newer format

Merge branch 'master' into BHV-10256-SungbaeCho

Conflicts:
	source/kernel/UiComponent.js
Merge pull request #796 from enyojs/BHV-10256-SungbaeCho

BHV-10256: optimize event bubbling using cached bubble target

Reviewed-By: Cole Davis (cole.davis@lge.com)