Add ToBoolean-conversion of constants in Crankshaft and use it when generating a branch based on ...

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 7547)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1114,9 +1114,9 @@
       return new LIsConstructCallAndBranch(TempRegister());
     } else {
       if (v->IsConstant()) {
-        if (HConstant::cast(v)->handle()->IsTrue()) {
+        if (HConstant::cast(v)->ToBoolean()) {
           return new LGoto(instr->FirstSuccessor()->block_id());
-        } else if (HConstant::cast(v)->handle()->IsFalse()) {
+        } else {
           return new LGoto(instr->SecondSuccessor()->block_id());
         }
       }