fix: empty captions menu when playing native hls

[dan-ziv]

Description of the Changes

Sometimes, when playing native hls on Safari, text tracks are not ready on loadeddata event. If this the case, we will wait for canplay event and parse the tracks right after.

CheckLists

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• test are passing in local environment
• Travis tests are passing (or test results are not worse than on master branch :))
• Docs have been updated

[OrenMe]

@dan-ziv the flow linter is failing the test, please fix