Small bonded atoms

[KatieWoe]

Test device:
Dell
Operating System:
Win 10
Browser:
firefox
Problem description:
For phetsims/qa#301 and phetsims/qa#302
The bonded atoms in the toolbox on the model screen seem smaller than normal.
Steps to reproduce:

1. Open the sim in Win 10 firefox.
2. Go to model screen
3. Compare to chrome

Screenshots:
Normal

Firefox

Troubleshooting information (do not edit):

Name: ‪Molecule Shapes: Basics‬
URL: https://phet-dev.colorado.edu/html/molecule-shapes-basics/1.2.0-rc.2/phet/molecule-shapes-basics_all_phet.html
Version: 1.2.0-rc.2 2019-03-28 11:22:39 UTC
Flags: pixelRatioScaling
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0
Language: en-US
Window: 1536x750
Pixel Ratio: 2.5/1
WebGL: WebGL 1.0
GLSL: WebGL GLSL ES 1.0
Vendor: Mozilla (Mozilla)
Vertex: attribs: 16 varying: 30 uniform: 4096
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 32767x32767
OES_texture_float: true
Dependencies JSON: {}

[kathy-phet]

Confirmed this bug. And it is not present in the currently published version. @jonathanolson - Can you take a look at what is causing this?

[KatieWoe]

Looks good in the two rcs