timebox: 1 hour
===Why are we doing this?
Tabs look ugly when stacked (shadows are too intense) and they use placeholder images, which we try to avoid since T218201.
===Suggested solution
A visual overhaul, tab behavior stays exactly the same.
| Before | After (w/ image) | After (w/o image) | After (multiple)
| {F28913502} | {F28913749} | {F28913751} | {F28913756}
Changes in written form:
- Reduce tab shadow to what鈥檚 specified on Zeplin
- Remove tab header placeholder image
- Change tab header and frame color to `paper_color`
- Add border-bottom to tab header when there鈥檚 no article image `tab_placeholder_text_color`
- Change tab view background color to `android:colorBackground`
馃憠 **[[ https://app.zeplin.io/project/57a120b91998d8977642a238/dashboard?seid=5ccc0a9343a94567de7b311e | Cleaner look for tabs ]] on Zeplin.**