Texture input field of blackboard in shader graph is clipped. Even default text "None (Texture)" or selected texture name is clipped.

Steps to reproduce:
1. Create a new project
2. Window > Package Manager > All > Shader Graph > Install
3. Project > Create > Shader > PBR Graph / Sub Graph / Unlit Graph
4. Open Shader Editor from inspector
5. Select "+" from Blackboard window > Texture
6. Observe that texture selection field is clipped.

Reproducible on:
Unity 2018.2.0b6, 2018.2.0b1, 2018.1.0f2, 2018.1.0b5

Note:
1. In 2018.3.0a1, PBR Graph / Sub Graph / Unlit Graph options are not available.
2. In 2018.2.0a8 to 2018.2.0a1, Package Manager is not included.
3. In 2018.1.0b4 and lower versions, Package Manager is not included.

Environment:
Mac 10.13 Windows 10