NavigationDrawer(Panel)looks semi-transparent

**Describe the bug**
NavigationDrawer(Panel) looks semi-transparent.

**To Reproduce**
Steps to reproduce the behavior:
1. Launch Meterial Gallery
2. Select NavigationDrawerPage Gallery

**Screenshots**
<img src="https://user-images.githubusercontent.com/20968023/91968555-c5813500-ed4f-11ea-91b1-e93f21f3df30.png" width="300" />

<img src="https://user-images.githubusercontent.com/20968023/91968666-eba6d500-ed4f-11ea-9ad1-3c0abcc57d7f.png" width="300" />



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NavigationDrawer(Panel)looks semi-transparent #60

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NavigationDrawer(Panel)looks semi-transparent #60

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions