Fix leaks in the embedder tests themselves.

fpdfsdk/src/fpdfformfill_embeddertest.cpp

 // Copyright 2015 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 #include "../../public/fpdf_formfill.h"
 #include "../../testing/embedder_test.h"
 #include "../../testing/embedder_test_mock_delegate.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using testing::_;
 using testing::Return;
 
 class FPDFFormFillEmbeddertest : public EmbedderTest {
 };
 
 TEST_F(FPDFFormFillEmbeddertest, FirstTest) {
   EmbedderTestMockDelegate mock;
   EXPECT_CALL(mock, Alert(_, _, _, _)).Times(0);
   EXPECT_CALL(mock, UnsupportedHandler(_)).Times(0);
   SetDelegate(&mock);
 
   EXPECT_TRUE(OpenDocument("testing/resources/hello_world.pdf"));
   FPDF_PAGE page = LoadPage(0);
   EXPECT_NE(nullptr, page);
+  UnloadPage(page);
 }