fix(DASH): fix memory leak with SegmentTimeline (#3039)

We found the issue within our app with the latest Chromecast CAF receiver update (November 22, 2020) that use Shaka 3.0.x. With our live stream containing 90 minutes of buffer, we notice high level of buffering issue with our customer.

It seems that the createUris callback was holding onto a parsing context in each reference.

Closes #3038

AUTHORS

@@ -23,6 +23,7 @@ Bonnier Broadcasting <*@bonnierbroadcasting.com>
 Bryan Huh <bhh1988@gmail.com>
 Code It <*@code-it.fr>
 Damien Deis <developer.deis@gmail.com>
+Dany L'Hébreux <danylhebreux@gmail.com>
 Esteban Dosztal <edosztal@gmail.com>
 Fadomire <fadomire@gmail.com>
 Google Inc. <*@google.com>

CONTRIBUTORS

@@ -35,6 +35,7 @@ Chad Assareh <assareh@google.com>
 Chris Fillmore <fillmore.chris@gmail.com>
 Costel Madalin Grecu <madalin.grecu@adswizz.com>
 Damien Deis <developer.deis@gmail.com>
+Dany L'Hébreux <danylhebreux@gmail.com>
 Donato Borrello <donato@jwplayer.com>
 Duc Pham <duc.pham@edgeware.tv>
 Esteban Dosztal <edosztal@gmail.com>

lib/dash/segment_template.js

@@ -465,16 +465,24 @@ shaka.dash.SegmentTemplate = class {
           info.unscaledPresentationTimeOffset;
       const repId = context.representation.id;
       const bandwidth = context.bandwidth || null;
+      const mediaTemplate = info.mediaTemplate;
+      const baseUris = context.representation.baseUris;
+
+      // This callback must not capture any non-local
+      // variables, such as info, context, etc.  Make
+      // sure any values you reference here have
+      // been assigned to local variables within the
+      // loop, or else we will end up with a leak.
       const createUris =
           () => {
             goog.asserts.assert(
-                info.mediaTemplate,
+                mediaTemplate,
                 'There should be a media template with a timeline');
             const mediaUri = MpdUtils.fillUriTemplate(
-                info.mediaTemplate, repId,
+                mediaTemplate, repId,
                 segmentReplacement, bandwidth || null, timeReplacement);
             return ManifestParserUtils
-                .resolveUris(context.representation.baseUris, [mediaUri])
+                .resolveUris(baseUris, [mediaUri])
                 .map((g) => {
                   return g.toString();
                 });