Removed useless Canonicalize implementations subsumed by dead code elimination.

src/hydrogen-instructions.cc

Index: src/hydrogen-instructions.cc
diff --git a/src/hydrogen-instructions.cc b/src/hydrogen-instructions.cc
index 72d3aab4944596cd1caf7d09a38f8829ca9d5528..feac1be0bcfcdf45f6c435f7899acd645d24e4e8 100644
--- a/src/hydrogen-instructions.cc
+++ b/src/hydrogen-instructions.cc
@@ -859,16 +859,6 @@ void HLoadFieldByIndex::PrintDataTo(StringStream* stream) {
 }
 
 
-HValue* HConstant::Canonicalize() {
-  return HasNoUses() ? NULL : this;
-}
-
-
-HValue* HTypeof::Canonicalize() {
-  return HasNoUses() ? NULL : this;
-}
-
-
 HValue* HBitwise::Canonicalize() {
   if (!representation().IsInteger32()) return this;
   // If x is an int32, then x & -1 == x, x | 0 == x and x ^ 0 == x.