How to capture screenshot of entire webpage in Android browser like I can take in my Desktop with Help of Firefox Addon called "Fireshot"?
Firefox Mobile or another browser would need to support this directly for such an extension to work. Do you need a screenshot, or do you just need to view pages offline? In the latter case, the answers to this question might help: Viewing web pages offline
Firefox Mobile + addon Fennec Screenshot does that job perfectly.
You can use browsers that support Add-ons. For example, I use Dolphin Browser and use the add-on called "Screen Cut" / "Dolphin Screen Cut" which allows freestyle screenshot so you can rearrange and measure a certain area of the screen if you so choose it over than a whole screen capture.
You can also use Maxthon Browser which supports this.