Adding a method to get the ratio of video length buffered compared to bufferingGoal

lib/player.js

@@ -2837,6 +2837,32 @@ shaka.Player = class extends shaka.util.FakeEventTarget {
     return this.config_;
   }
 
+  /**
+   * Returns the ratio of video length buffered compared to buffering Goal
+   * @return {number}
+   * @export
+   */
+  getBufferFullness() {
+    const bufferedLength_ = this.video_ ?
+        this.video_.buffered.length : 0;
+    const bufferedEnd_ =
+        bufferedLength_ ? this.video_.buffered.end(bufferedLength_ - 1) : 0;
+    const bufferingGoal_ = this.getConfiguration().streaming.bufferingGoal;
+    const lengthToBeBuffered = this.video_ ? Math.min(this.video_.currentTime +
+        bufferingGoal_, this.seekRange().end) : 0;
+
+    if (this.video_) {
+      if (bufferedEnd_ >= lengthToBeBuffered) {
+        return 1;
+      } else if (bufferedEnd_ <= this.video_.currentTime) {
+        return 0;
+      } else if (bufferedEnd_ < lengthToBeBuffered) {
+        return ((bufferedEnd_ - this.video_.currentTime) / bufferingGoal_);
+      }
+    }
+    return 0;
+  }
+
   /**
    * Reset configuration to default.
    * @export