Merge to XFA: Add fpdf_edit basic creation embedder test.

Original Review URL: https://codereview.chromium.org/1554133003 .
(cherry picked from commit d368261cc8d604286e29ca6358700e6bb051dcaa)

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1567643002 .
diff --git a/testing/embedder_test.h b/testing/embedder_test.h
index a544f26..c780cca 100644
--- a/testing/embedder_test.h
+++ b/testing/embedder_test.h
@@ -78,6 +78,10 @@
   FPDF_DOCUMENT document() { return document_; }
   FPDF_FORMHANDLE form_handle() { return form_handle_; }
 
+  // Create an empty document, and its form fill environment. Returns true
+  // on success or false on failure.
+  virtual bool CreateEmptyDocument();
+
   // Open the document specified by |filename|, and create its form fill
   // environment, or return false on failure.
   // The filename is relative to the test data directory where we store all the
@@ -107,6 +111,8 @@
   virtual void UnloadPage(FPDF_PAGE page);
 
  protected:
+  void SetupFormFillEnvironment();
+
   Delegate* delegate_;
   std::unique_ptr<Delegate> default_delegate_;
   FPDF_DOCUMENT document_;