Remove the redundant load on every context lookup.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 1d5cefcb4996e7e0fa1f5a0e2263854a555937b3..092601dd1355ded4d7cbbc829a03bd95b0ac9a70 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1685,13 +1685,15 @@ LInstruction* LChunkBuilder::DoLoadContextSlot(HLoadContextSlot* instr) {
 
 
 LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
-  LOperand* context = UseTempRegister(instr->context());
+  LOperand* context;
   LOperand* value;
   LOperand* temp;
   if (instr->NeedsWriteBarrier()) {
+    context = UseTempRegister(instr->context());
     value = UseTempRegister(instr->value());
     temp = TempRegister();
   } else {
+    context = UseRegister(instr->context());
     value = UseRegister(instr->value());
     temp = NULL;
   }