Summary:It didn't work for a few reason. First, the drawer view NEEDS to have a background color or no shadow will ever render. Second, we need to use the `setDrawerElevation` method instead of `setElevation` for DrawerLayout. Finally we need to actually pass the style value (maybe we could just pass elevation but I don't really think it can cause any issues) down to the native component as it is not the case at the moment.
I also added a default style to elevation of 16 which is the standard for material design according to https://www.google.com/design/spec/patterns/navigation-drawer.html#navigation-drawer-specs. I could also default it to 0 so it keeps the same appearance as before but I think it looks better this way.
Closes#6022
**Test plan**
Tested using the DrawerLayout in the UIExplorer app.
Before, elevation 0
<img width="420" alt="screen shot 2016-02-23 at 1 55 42 am" src="https://cloud.githubusercontent.com/assets/2677334/13244000/008afdb2-d9d1-11e5-95b8-9c345ea0ea8d.png">
After, elevation
Closes https://github.com/facebook/react-native/pull/6100
Reviewed By: bestander
Differential Revision: D3012242
Pulled By: lexs
fb-gh-sync-id: 4967d7ec920f0229d823032ba95c8a3cace329c6
shipit-source-id: 4967d7ec920f0229d823032ba95c8a3cace329c6
61483aa15d
