Setting editor active item's border clipped at small widths

[mjbvz]

Issue Type: Bug

1. Open settings editor in a narrow editor
2. Click on a setting

Bug
Notice the active border appears clipped on the far right edge

Here's what it should look like:

VS Code version: code-oss-dev 1.25.0 (Commit unknown, Date unknown)
OS version: Darwin x64 17.5.0

System Info

Item	Value
CPUs	Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz (8 x 2200)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on native_gpu_memory_buffers: enabled rasterization: enabled video_decode: enabled video_encode: enabled vpx_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	2, 2, 2
Memory (System)	16.00GB (1.14GB free)
Process Argv	/Users/matb/projects/vscode/.build/electron/Code - OSS.app/Contents/MacOS/Electron .
Screen Reader	no
VM	17%

Extensions (1)

Extension	Author (truncated)	Version
cat-coding	ms-	0.0.1

[mjbvz]

The border is actually there but the lack of padding makes it looked like it is being clipped