Fix SourceBuffer.remove() calls for IE11

On IE11, SourceBuffer.remove(start, Number.POSITIVE_INFINITY) triggers
an 'updateend' event, but does not seem to remove anything.  The same
is true if we swap Number.MAX_VALUE for Number.POSITIVE_INFINITY.
MediaSource.duration does seem to work, though, to remove all content
from buffer.

Fixes #251

Change-Id: I67152f8deceb8926ae1376fdccf73db0c62d0a3e

lib/media/source_buffer_manager.js

@@ -562,7 +562,7 @@ shaka.media.SourceBufferManager.prototype.clear_ = function() {
 
   try {
     // This will trigger an 'updateend' event.
-    this.sourceBuffer_.remove(0, Number.POSITIVE_INFINITY);
+    this.sourceBuffer_.remove(0, this.mediaSource_.duration);
   } catch (exception) {
     return Promise.reject(exception);
   }
@@ -608,7 +608,7 @@ shaka.media.SourceBufferManager.prototype.clearAfter_ = function(timestamp) {
     // This will trigger an 'updateend' event.
     this.sourceBuffer_.remove(
         this.inserted_[index + 1].startTime,
-        Number.POSITIVE_INFINITY);
+        this.mediaSource_.duration);
   } catch (exception) {
     return Promise.reject(exception);
   }