Make it a compile error to use a crash key with no variable name.

base/debug/crash_logging_unittest.cc

Index: base/debug/crash_logging_unittest.cc
diff --git a/base/debug/crash_logging_unittest.cc b/base/debug/crash_logging_unittest.cc
index 5197c03e272ccdec2dd38457ffa115bd59786ca5..20e95c95e57e558289cadc8175f0f8f9690b3f22 100644
--- a/base/debug/crash_logging_unittest.cc
+++ b/base/debug/crash_logging_unittest.cc
@@ -115,6 +115,7 @@ TEST_F(CrashLoggingTest, ScopedCrashKey) {
   EXPECT_TRUE(key_values_->end() == key_values_->find(kTestKey));
   {
     base::debug::ScopedCrashKey scoped_crash_key(kTestKey, "value");
+    base::debug::ScopedCrashKey(kTestKey, "with no name");
     EXPECT_EQ("value", (*key_values_)[kTestKey]);
     EXPECT_EQ(1u, key_values_->size());
   }