tools/gn: Pass clang-modernize -use-nullptr over it.

tools/gn/value_unittest.cc

Index: tools/gn/value_unittest.cc
diff --git a/tools/gn/value_unittest.cc b/tools/gn/value_unittest.cc
index 3fa990d4a28e915190c927f4fd36153f0a8c9b02..9cbdaa2dda3699cede165227ec355163c4bcd85c 100644
--- a/tools/gn/value_unittest.cc
+++ b/tools/gn/value_unittest.cc
@@ -7,7 +7,7 @@
 #include "tools/gn/value.h"
 
 TEST(Value, ToString) {
-  Value strval(NULL, "hi\" $me\\you\\$\\\"");
+  Value strval(nullptr, "hi\" $me\\you\\$\\\"");
   EXPECT_EQ("hi\" $me\\you\\$\\\"", strval.ToString(false));
   EXPECT_EQ("\"hi\\\" \\$me\\you\\\\\\$\\\\\\\"\"", strval.ToString(true));
 
@@ -15,11 +15,11 @@ TEST(Value, ToString) {
   EXPECT_EQ("<void>", Value().ToString(false));
 
   // Test lists, bools, and ints.
-  Value listval(NULL, Value::LIST);
-  listval.list_value().push_back(Value(NULL, "hi\"me"));
-  listval.list_value().push_back(Value(NULL, true));
-  listval.list_value().push_back(Value(NULL, false));
-  listval.list_value().push_back(Value(NULL, static_cast<int64>(42)));
+  Value listval(nullptr, Value::LIST);
+  listval.list_value().push_back(Value(nullptr, "hi\"me"));
+  listval.list_value().push_back(Value(nullptr, true));
+  listval.list_value().push_back(Value(nullptr, false));
+  listval.list_value().push_back(Value(nullptr, static_cast<int64>(42)));
   // Printing lists always causes embedded strings to be quoted (ignoring the
   // quote flag), or else they wouldn't make much sense.
   EXPECT_EQ("[\"hi\\\"me\", true, false, 42]", listval.ToString(false));
@@ -28,11 +28,11 @@ TEST(Value, ToString) {
   // Scopes.
   TestWithScope setup;
   Scope* scope = new Scope(setup.scope());
-  Value scopeval(NULL, scoped_ptr<Scope>(scope));
+  Value scopeval(nullptr, scoped_ptr<Scope>(scope));
   EXPECT_EQ("{ }", scopeval.ToString(false));
 
-  scope->SetValue("a", Value(NULL, static_cast<int64>(42)), NULL);
-  scope->SetValue("b", Value(NULL, "hello, world"), NULL);
+  scope->SetValue("a", Value(nullptr, static_cast<int64>(42)), nullptr);
+  scope->SetValue("b", Value(nullptr, "hello, world"), nullptr);
   EXPECT_EQ("{\n  a = 42\n  b = \"hello, world\"\n}", scopeval.ToString(false));
 }