Extract hardcoded error strings into a single place and replace them with enum.

src/ia32/ic-ia32.cc

Index: src/ia32/ic-ia32.cc
diff --git a/src/ia32/ic-ia32.cc b/src/ia32/ic-ia32.cc
index bf0c80b2b4682655f6931857936226c72e38cdb1..1e0f14e7687b1ed66000753311d99bab1acb3c5f 100644
--- a/src/ia32/ic-ia32.cc
+++ b/src/ia32/ic-ia32.cc
@@ -483,7 +483,7 @@ void KeyedLoadIC::GenerateGeneric(MacroAssembler* masm) {
   // based on 32 bits of the map pointer and the string hash.
   if (FLAG_debug_code) {
     __ cmp(eax, FieldOperand(edx, HeapObject::kMapOffset));
-    __ Check(equal, "Map is no longer in eax.");
+    __ Check(equal, kMapIsNoLongerInEax);
   }
   __ mov(ebx, eax);  // Keep the map around for later.
   __ shr(eax, KeyedLookupCache::kMapHashShift);