Remove FLAG_opt_safe_uint32_operations.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 9572a33ad87772595ef0f5f5d0d7e61f8071d15a..541d37ad6e66c3c48d262514bc8249eadecc821b 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -722,11 +722,7 @@ LInstruction* LChunkBuilder::DoShift(Token::Value op,
     // Shift operations can only deoptimize if we do a logical shift by 0 and
     // the result cannot be truncated to int32.
     if (op == Token::SHR && constant_value == 0) {
-      if (FLAG_opt_safe_uint32_operations) {
-        does_deopt = !instr->CheckFlag(HInstruction::kUint32);
-      } else {
-        does_deopt = !instr->CheckUsesForFlag(HValue::kTruncatingToInt32);
-      }
+      does_deopt = !instr->CheckFlag(HInstruction::kUint32);
     }
 
     LInstruction* result =