Reproduction Steps:
1. Import attached project.
2. Open "Test" scene.
3. Enter Play mode.
4. Observe how AudioSource.time is equal to 0 before the audio clip begins.
5. Build and Run a WebGL build.

Expected result: AudioSource.time is equal to 0, as it is in the Editor.
Actual result: AudioSource.time is equal to a random value before the audio clip starts and resets it. (usually the value is 11.052)

Reproducible with: 5.4.5f1, 5.5.3p2, 5.6.0p3, 2017.1.0b2