Fixes for re-enabling more MSVC level 4 warnings: chrome/ edition

chrome/utility/media_galleries/pmp_column_reader_unittest.cc

Index: chrome/utility/media_galleries/pmp_column_reader_unittest.cc
diff --git a/chrome/utility/media_galleries/pmp_column_reader_unittest.cc b/chrome/utility/media_galleries/pmp_column_reader_unittest.cc
index f4f178235c9b6d220c7c5e92a98d43f3a2b44cb0..7c9bb6f3fce31d0e478dfec1d3a74a30bc5eb908 100644
--- a/chrome/utility/media_galleries/pmp_column_reader_unittest.cc
+++ b/chrome/utility/media_galleries/pmp_column_reader_unittest.cc
@@ -140,7 +140,7 @@ TEST(PmpColumnReaderTest, HeaderParsingAndValidation) {
   PmpColumnReader reader_bad_magic_bytes;
   std::vector<char> bad_magic_bytes =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  bad_magic_bytes[0] = (char)0xff;
+  bad_magic_bytes[0] = static_cast<char>(-128);

[Peter Kasting, 2014/07/07 20:55:46]

0xff is considered by the compiler to be a positive value, and thus is larger
than what a signed char can hold, triggering a "constant truncated" warning.

To me, this suggests that this code should be using uint8_t, or at least
unsigned char, instead.  However, making that change turns out to be fairly
far-ranging (we have various routines in Chrome that use "vector<char>" to mean
"string of bytes"), so eventually I gave up and just made the change here.

   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_bad_magic_bytes,
                                          bad_magic_bytes,
                                          PMP_TYPE_STRING));
@@ -148,7 +148,7 @@ TEST(PmpColumnReaderTest, HeaderParsingAndValidation) {
   PmpColumnReader reader_inconsistent_types;
   std::vector<char> inconsistent_type =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  inconsistent_type[kPmpFieldType1Offset] = (char)0xff;
+  inconsistent_type[kPmpFieldType1Offset] = static_cast<char>(-128);
   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_inconsistent_types,
                                          inconsistent_type,
                                          PMP_TYPE_STRING));
@@ -156,8 +156,8 @@ TEST(PmpColumnReaderTest, HeaderParsingAndValidation) {
   PmpColumnReader reader_invalid_type;
   std::vector<char> invalid_type =
       PmpTestUtil::MakeHeader(PMP_TYPE_STRING, 0);
-  invalid_type[kPmpFieldType1Offset] = (char)0xff;
-  invalid_type[kPmpFieldType2Offset] = (char)0xff;
+  invalid_type[kPmpFieldType1Offset] = static_cast<char>(-128);
+  invalid_type[kPmpFieldType2Offset] = static_cast<char>(-128);
   EXPECT_FALSE(InitColumnReaderFromBytes(&reader_invalid_type,
                                          invalid_type,
                                          PMP_TYPE_STRING));