Handle empty objects in IsSameTextObject() and free from warning
Handle empty objects in IsSameTextObject() and free from warning

When both text objects have no items, directly return TRUE;
The last if statement moved inside loop to make the intent more
obvious and free from warning (msvc warns using potentially
uninitialized var itemPer)

R=jun_fang@foxitsoftware.com

Review URL: https://codereview.chromium.org/1815453002 .

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