Externalize deoptimization reasons.

src/disassembler.cc

Index: src/disassembler.cc
diff --git a/src/disassembler.cc b/src/disassembler.cc
index bedff451e9f87d0e4bcaae5a21c5b4ed9b6d34b3..7940220bf60aa5c14821c6d9ecd7fc158931cc49 100644
--- a/src/disassembler.cc
+++ b/src/disassembler.cc
@@ -173,6 +173,11 @@ static int DecodeIt(Isolate* isolate, std::ostream* os,
         } else {
           out.AddFormatted("    ;; debug: position %d", relocinfo.data());
         }
+      } else if (rmode == RelocInfo::DEOPT_REASON) {
+        Deoptimizer::DeoptReason reason =
+            static_cast<Deoptimizer::DeoptReason>(relocinfo.data());
+        out.AddFormatted("    ;; debug: deopt reason '%s'",
+                         Deoptimizer::GetDeoptReason(reason));
       } else if (rmode == RelocInfo::EMBEDDED_OBJECT) {
         HeapStringAllocator allocator;
         StringStream accumulator(&allocator);