Add Unit test cases for Viewer. Mock Http related class.
Add Unit test cases for Viewer. Mock Http related class.

sguan-actuate/birt,Charling-Huang/birt,Charling-Huang/birt,rrimmana/birt-1,rrimmana/birt-1,rrimmana/birt-1,sguan-actuate/birt,sguan-actuate/birt,sguan-actuate/birt,sguan-actuate/birt,Charling-Huang/birt,Charling-Huang/birt,rrimmana/birt-1,Charling-Huang/birt,rrimmana/birt-1