Fix the code that causes warnings

core/fpdfapi/fpdf_parser/cpdf_array_unittest.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 "core/fpdfapi/fpdf_parser/include/cpdf_array.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_number.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_reference.h"
 
 #include <memory>
 
@@ skipping 58 matching lines @@
   }
   {
     // When the position to insert is beyond the upper bound,
     // an element is inserted at that position while other unfilled
     // positions have nullptr.
     int elems[] = {1, 2};
     ScopedArray arr(new CPDF_Array);
     for (size_t i = 0; i < FX_ArraySize(elems); ++i)
       arr->InsertAt(i, new CPDF_Number(elems[i]));
     arr->InsertAt(10, new CPDF_Number(10));
-    EXPECT_EQ(11, arr->GetCount());
+    EXPECT_EQ(11u, arr->GetCount());
     for (size_t i = 0; i < FX_ArraySize(elems); ++i)
       EXPECT_EQ(elems[i], arr->GetIntegerAt(i));
     for (size_t i = FX_ArraySize(elems); i < 10; ++i)
       EXPECT_EQ(nullptr, arr->GetObjectAt(i));
     EXPECT_EQ(10, arr->GetIntegerAt(10));
   }
 }
 
 TEST(cpdf_array, Clone) {
   {
@@ skipping 82 matching lines @@
 TEST(cpdf_array, Iterator) {
   int elems[] = {-23, -11,     3,         455,   2345877,
                  0,   7895330, -12564334, 10000, -100000};
   ScopedArray arr(new CPDF_Array);
   for (size_t i = 0; i < FX_ArraySize(elems); ++i)
     arr->InsertAt(i, new CPDF_Number(elems[i]));
   size_t index = 0;
   for (const auto& it : *arr)
     EXPECT_EQ(elems[index++], it->AsNumber()->GetInteger());
 }