Introduce GifDemuxDecodeWrapper

Reviewed By: ricky8554

Differential Revision: D50593355

fbshipit-source-id: e74773641c6967ec6805b6ec6230a9283c1b3ca8

animated-drawable/src/main/java/com/facebook/fresco/animation/drawable/AnimatedDrawable2.java

@@ -390,6 +390,16 @@ public int getFrameCount() {
     return mAnimationBackend == null ? 0 : mAnimationBackend.getFrameCount();
   }
 
+  /**
+   * Get the duration of a specific frame. If not animation backend is set, 0 will be returned.
+   *
+   * @param frameNumber the requested frame
+   * @return the duration of the frame
+   */
+  public int getFrameDurationMs(int frameNumber) {
+    return mAnimationBackend == null ? 0 : mAnimationBackend.getFrameDurationMs(frameNumber);
+  }
+
   /**
    * Get the loop count of the animation. The returned value is either
    * [AnimationInformation#LOOP_COUNT_INFINITE] if the animation is repeated infinitely or a