Add stable id to PaintImage.

cc/test/fake_content_layer_client.cc

Index: cc/test/fake_content_layer_client.cc
diff --git a/cc/test/fake_content_layer_client.cc b/cc/test/fake_content_layer_client.cc
index 1881a9784342379e69ebd5d87f4be569d0a2c8f4..d6080740ee7cbc80dc2177ed04498bcf6a757613 100644
--- a/cc/test/fake_content_layer_client.cc
+++ b/cc/test/fake_content_layer_client.cc
@@ -71,8 +71,8 @@ FakeContentLayerClient::PaintContentsToDisplayList(
     }
     PaintCanvas* canvas =
         recorder.beginRecording(it->image->width(), it->image->height());
-    canvas->drawImage(PaintImage(it->image), it->point.x(), it->point.y(),
-                      &it->flags);
+    canvas->drawImage(PaintImage(PaintImage::GetNextId(), it->image),
+                      it->point.x(), it->point.y(), &it->flags);
     display_list->CreateAndAppendDrawingItem<DrawingDisplayItem>(
         PaintableRegion(), recorder.finishRecordingAsPicture());
     if (!it->transform.IsIdentity()) {