SkPDF: flip saveLayer rightside up

src/pdf/SkPDFFormXObject.cpp

 /*
  * Copyright 2010 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkPDFFormXObject.h"
+#include "SkPDFUtils.h"
 
 sk_sp<SkPDFObject> SkPDFMakeFormXObject(std::unique_ptr<SkStreamAsset> content,
                                         sk_sp<SkPDFArray> mediaBox,
                                         sk_sp<SkPDFDict> resourceDict,
+                                        const SkMatrix& inverseTransform,
                                         const char* colorSpace) {
     auto form = sk_make_sp<SkPDFStream>(std::move(content));
     form->insertName("Type", "XObject");
     form->insertName("Subtype", "Form");
+    if (!inverseTransform.isIdentity()) {
+        form->insertObject("Matrix",
+                           SkPDFUtils::MatrixToArray(inverseTransform));
+    }
     form->insertObject("Resources", std::move(resourceDict));
     form->insertObject("BBox", std::move(mediaBox));
 
     // Right now FormXObject is only used for saveLayer, which implies
     // isolated blending.  Do this conditionally if that changes.
     // TODO(halcanary): Is this comment obsolete, since we use it for
     // alpha masks?
     auto group = sk_make_sp<SkPDFDict>("Group");
     group->insertName("S", "Transparency");
     if (colorSpace != nullptr) {
         group->insertName("CS", colorSpace);
     }
     group->insertBool("I", true);  // Isolated.
     form->insertObject("Group", std::move(group));
     return form;
 }