Introduce a class to carry around a deoptimization reason.

src/lithium-codegen.cc

Index: src/lithium-codegen.cc
diff --git a/src/lithium-codegen.cc b/src/lithium-codegen.cc
index 86401167aca7a953c21a3f7c8d6d4d9187e19256..bc73bb938fa94f08d1937f7fe746e249692d4115 100644
--- a/src/lithium-codegen.cc
+++ b/src/lithium-codegen.cc
@@ -147,9 +147,9 @@ void LCodeGenBase::Comment(const char* format, ...) {
 }
 
 
-void LCodeGenBase::DeoptComment(const char* mnemonic, const char* reason) {
-  Comment(";;; deoptimize %s: %s", mnemonic,
-          reason == NULL ? "unknown reason" : reason);
+void LCodeGenBase::DeoptComment(const Deoptimizer::Reason& reason) {
+  Comment(";;; deoptimize %s: %s", reason.mnemonic,
+          reason.detail == NULL ? "unknown reason" : reason.detail);
 }