To reproduce:
1) Open attached project and scene
2) Play it
Expected: Try copying this bit of random Chinese hieroglyphs into the input field in scene: 也还是无法
It should copy in okay. Same happens on Windows Standalone build

Actual:
3) Build and run it on WebGL
4) Try doing the same as Expected step - this time no text appears

Couldn't test properly using the Chinese language in Windows as I could only do pinyin typing.

Reproduced in 2017.1.0f3, 2017.2.0f3, 2018.1.0a7

Reproduced in Chrome 62.0.3202.94 (Official Build) (64-bit) and Firefox 57.0.2 (64-bit)