Modify ALLOW_UNUSED to allow enabling unused local warnings on MSVC.

This splits the macro into two:

int a = 1;
ALLOW_UNUSED_LOCAL(a);

and

typedef Foo Bar ALLOW_UNUSED_TYPE;
void foo() ALLOW_UNUSED_TYPE;  // ALLOW_UNUSED_TYPE_OR_FUNC seemed too verbose

This matches changes that have already been made in Blink.

BUG=81439
TEST=none
TBR=ben

Review URL: https://codereview.chromium.org/650393002

Cr-Commit-Position: refs/heads/master@{#300014}


CrOS-Libchrome-Original-Commit: 99867ef78bf14ad37e263860248d0a2d61b51a73
diff --git a/base/logging_unittest.cc b/base/logging_unittest.cc
index 6ebe32e..95a16f2 100644
--- a/base/logging_unittest.cc
+++ b/base/logging_unittest.cc
@@ -240,7 +240,8 @@
 // looking in the global namespace.
 namespace nested_test {
   class Streamable {};
-  ALLOW_UNUSED std::ostream& operator<<(std::ostream& out, const Streamable&) {
+  ALLOW_UNUSED_TYPE std::ostream& operator<<(std::ostream& out,
+                                             const Streamable&) {
     return out << "Streamable";
   }
   TEST_F(LoggingTest, StreamingWstringFindsCorrectOperator) {