v1.x: Improve DASH parser performance w/ large timeshift depths

[joeyparrish]

In #405, we improved DASH parser performance for large timeshift depths by deferring filling URI templates. Investigate whether or not this can be easily implemented in v1.6.x as well.

[joeyparrish]

@torerikal mentioned that this fix was in their fork: vimond/shaka-player@adbcdb5

@torerikal, @janouskovec, any interest in cleaning it up and creating a PR?

I think it's a good start, but the subclass should call the base class's constructor instead of re-creating all of its members. There also doesn't seem to be any need to make everything protected, just make urls non-const.

[janouskovec]

In fact no need creating PR for me, because I already fixed the issue in my local repository and push now to my fork: janouskovec@Deferring filling URI templates.

[joeyparrish]

Okay, closing for lack of interest. If anybody wants to patch v1 for this, please feel free to reply and we can reopen.