clang/win: Let some chromium_code targets build with -Wextra.

base/win/iunknown_impl_unittest.cc

Index: base/win/iunknown_impl_unittest.cc
diff --git a/base/win/iunknown_impl_unittest.cc b/base/win/iunknown_impl_unittest.cc
index 874a43a39a99a24c4fae13fdf7e7cf6b261cf4af..c6c3539037e5cc2ebb4270fe62370c6e4f758041 100644
--- a/base/win/iunknown_impl_unittest.cc
+++ b/base/win/iunknown_impl_unittest.cc
@@ -30,8 +30,8 @@ TEST(IUnknownImplTest, IUnknownImpl) {
 
   EXPECT_EQ(1, TestIUnknownImplSubclass::instance_count);
 
-  EXPECT_EQ(1, u->AddRef());
-  EXPECT_EQ(1, u->AddRef());
+  EXPECT_EQ(1u, u->AddRef());
+  EXPECT_EQ(1u, u->AddRef());
 
   IUnknown* other = NULL;
   EXPECT_EQ(E_NOINTERFACE, u->QueryInterface(
@@ -40,8 +40,8 @@ TEST(IUnknownImplTest, IUnknownImpl) {
       IID_IUnknown, reinterpret_cast<void**>(&other)));
   other->Release();
 
-  EXPECT_EQ(1, u->Release());
-  EXPECT_EQ(0, u->Release());
+  EXPECT_EQ(1u, u->Release());
+  EXPECT_EQ(0u, u->Release());
   EXPECT_EQ(0, TestIUnknownImplSubclass::instance_count);
 }