Implement AImageDecoder_isAnimated

Bug: 160984428
Test: Ie98a7e80c2d0d6101bdf0ac3549a1fa6581aeba6
Change-Id: Iab70514cda54955368cedb472d84f89763569166
diff --git a/native/graphics/jni/imagedecoder.cpp b/native/graphics/jni/imagedecoder.cpp
index 56f3906..23035b6 100644
--- a/native/graphics/jni/imagedecoder.cpp
+++ b/native/graphics/jni/imagedecoder.cpp
@@ -346,3 +346,10 @@
 void AImageDecoder_delete(AImageDecoder* decoder) {
     delete toDecoder(decoder);
 }
+
+bool AImageDecoder_isAnimated(AImageDecoder* decoder) {
+    if (!decoder) return false;
+
+    ImageDecoder* imageDecoder = toDecoder(decoder);
+    return imageDecoder->mCodec->codec()->getFrameCount() > 1;
+}