Merge sub-device annotations in SkPDFDevice::drawDevice()

gm/annotated_text.cpp

Index: gm/annotated_text.cpp
diff --git a/gm/annotated_text.cpp b/gm/annotated_text.cpp
index 7126206eeb96b344d53fd6ffc7e23cdb0616099e..30f67b0201bf7fbb5c19fce622bbc27e6f546ce8 100644
--- a/gm/annotated_text.cpp
+++ b/gm/annotated_text.cpp
@@ -34,7 +34,8 @@ DEF_SIMPLE_GM(annotated_text, canvas, 512, 512) {
     const char text[] = "Click this link!";
     const char url[] = "https://www.google.com/";
     draw_url_annotated_text_with_box(canvas, text, 200.0f, 80.0f, p, url);
-    SkAutoCanvasRestore autoCanvasRestore2(canvas, true);
+    canvas->saveLayer(nullptr, nullptr);
     canvas->rotate(90);
     draw_url_annotated_text_with_box(canvas, text, 150.0f, -55.0f, p, url);
+    canvas->restore();
 }