Code change to avoid signed/unsigned mismatch warnings

fpdfsdk/fpdfsave_embeddertest.cpp

 // Copyright 2016 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 <string.h>
 
 #include "core/fxcrt/include/fx_string.h"
 #include "public/fpdf_save.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/fx_string_testhelpers.h"
 #include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/test_support.h"
 
 class FPDFSaveEmbedderTest : public EmbedderTest, public TestSaver {};
 
 TEST_F(FPDFSaveEmbedderTest, SaveSimpleDoc) {
   EXPECT_TRUE(OpenDocument("hello_world.pdf"));
   EXPECT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
   EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.7\r\n"));
-  EXPECT_EQ(843, GetString().length());
+  EXPECT_EQ(843u, GetString().length());
 }
 
 TEST_F(FPDFSaveEmbedderTest, SaveSimpleDocWithVersion) {
   EXPECT_TRUE(OpenDocument("hello_world.pdf"));
   EXPECT_TRUE(FPDF_SaveWithVersion(document(), this, 0, 14));
   EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.4\r\n"));
-  EXPECT_EQ(843, GetString().length());
+  EXPECT_EQ(843u, GetString().length());
 }
 
 TEST_F(FPDFSaveEmbedderTest, SaveSimpleDocWithBadVersion) {
   EXPECT_TRUE(OpenDocument("hello_world.pdf"));
   EXPECT_TRUE(FPDF_SaveWithVersion(document(), this, 0, -1));
   EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.7\r\n"));
 
   ClearString();
   EXPECT_TRUE(FPDF_SaveWithVersion(document(), this, 0, 0));
   EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.7\r\n"));
 
   ClearString();
   EXPECT_TRUE(FPDF_SaveWithVersion(document(), this, 0, 18));
   EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.7\r\n"));
 }
 
 TEST_F(FPDFSaveEmbedderTest, BUG_342) {
   EXPECT_TRUE(OpenDocument("hello_world.pdf"));
   EXPECT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
   EXPECT_THAT(GetString(), testing::HasSubstr("0000000000 65535 f\r\n"));
   EXPECT_THAT(GetString(),
               testing::Not(testing::HasSubstr("0000000000 65536 f\r\n")));
 }