feat: Support customizing clearBuffers and safeMargin when select var…

…iants by label (shaka-project#4770)

Currently, selectVariantsByLabel doesn't support customizing
clearBuffers and safeMargin. This pr is to change the function
signature, so that we'll able to decide if we want to keep some amount
of buffer when we change track.

AUTHORS

@@ -88,6 +88,7 @@ ViacomCBS <*@viacomcbs.com>
 Vincent Valot <valot.vince@gmail.com>
 V-Nova Limited <*@v-nova.com>
 Wayne Morgan <wayne.morgan.dev@gmail.com>
+Wen Ren <renwen0615@gmail.com>
 Raymond Cheng <raycheng100@gmail.com>
 Blue Billywig <*@bluebillywig.com>
 João Nabais <jlnabais@gmail.com>

CONTRIBUTORS

@@ -127,6 +127,7 @@ Vignesh Venkatasubramanian <vigneshv@google.com>
 Vincent Valot <valot.vince@gmail.com>
 Vinod Balakrishnan <vinod.balakrishnan@v-nova.com>
 Wayne Morgan <wayne.morgan.dev@gmail.com>
+Wen Ren <renwen0615@gmail.com>
 Yohann Connell <robinconnell@google.com>
 Raymond Cheng <raycheng100@gmail.com>
 Janroel Koppen <j.koppen@bluebillywig.com>

lib/player.js

@@ -4242,9 +4242,15 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    * are expected to have the same variant.audio.
    *
    * @param {string} label
+   * @param {boolean=} clearBuffer Optional clear buffer or not when
+   *  switch to new variant
+   *  Defaults to true if not provided
+   * @param {number=} safeMargin Optional amount of buffer (in seconds) to
+   *   retain when clearing the buffer.
+   *   Defaults to 0 if not provided. Ignored if clearBuffer is false.
    * @export
    */
-  selectVariantsByLabel(label) {
+  selectVariantsByLabel(label, clearBuffer = true, safeMargin = 0) {
     if (this.manifest_ && this.playhead_) {
       let firstVariantWithLabel = null;
       for (const variant of this.manifest_.variants) {
@@ -4268,7 +4274,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
           new shaka.media.PreferenceBasedCriteria(
               firstVariantWithLabel.language, '', 0, label);
 
-      this.chooseVariantAndSwitch_();
+      this.chooseVariantAndSwitch_(clearBuffer, safeMargin);
     }
   }
 
@@ -5713,9 +5719,15 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
    * Called after a config change, a key status event, or an explicit language
    * change.
    *
+   * @param {boolean=} clearBuffer Optional clear buffer or not when
+   *  switch to new variant
+   *  Defaults to true if not provided
+   * @param {number=} safeMargin Optional amount of buffer (in seconds) to
+   *   retain when clearing the buffer.
+   *   Defaults to 0 if not provided. Ignored if clearBuffer is false.
    * @private
    */
-  chooseVariantAndSwitch_() {
+  chooseVariantAndSwitch_(clearBuffer = true, safeMargin = 0) {
     goog.asserts.assert(this.config_, 'Must not be destroyed');
 
     // Because we're running this after a config change (manual language
@@ -5724,7 +5736,7 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     const chosenVariant = this.chooseVariant_();
     if (chosenVariant) {
       this.switchVariant_(chosenVariant, /* fromAdaptation= */ true,
-          /* clearBuffers= */ true, /* safeMargin= */ 0);
+          clearBuffer, safeMargin);
     }
   }