Remove FLAG_opt_safe_uint32_operations.

src/mips64/lithium-mips64.cc

Index: src/mips64/lithium-mips64.cc
diff --git a/src/mips64/lithium-mips64.cc b/src/mips64/lithium-mips64.cc
index 9ebe74e058a83127e7c84c46e829f1cab3aae2d0..664fdd0846f017e12ecf010d5d792713fc481730 100644
--- a/src/mips64/lithium-mips64.cc
+++ b/src/mips64/lithium-mips64.cc
@@ -706,11 +706,7 @@ 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 =