Refine surrounding text logic and test case readability.

1. Follow up refinement for CL[1].
2. Test case to verify the InitialSurroundingText parcel
wrapping/unwrapping logic.

[1] c486acc4d29a0e441ddcd05b3fc0c919aee7fbd0, Ie04f2349b1157408aa8ed9044aea12ce99132cb4

Bug: 148035211
Test: atest FrameworksCoreTests:EditorInfoTest
Change-Id: I9609b8a7dabb6285ed673cb0890bb3019e3b7caa
2 files changed