Enable preaging of code objects when --optimize-for-size.

src/arm/lithium-codegen-arm.cc

Index: src/arm/lithium-codegen-arm.cc
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 801c30bbdf606a466758fae3c54d8ec35c003e05..b8037415e67a0ba1a575913b189d6b5e60089c0c 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -143,10 +143,18 @@ bool LCodeGen::GeneratePrologue() {
           masm_, kNoCodeAgeSequenceLength * Assembler::kInstrSize);
       // The following three instructions must remain together and unmodified
       // for code aging to work properly.
-      __ stm(db_w, sp, r1.bit() | cp.bit() | fp.bit() | lr.bit());
-      __ nop(ip.code());
-      // Adjust FP to point to saved FP.
-      __ add(fp, sp, Operand(2 * kPointerSize));
+      if (FLAG_optimize_for_size && FLAG_age_code) {
+        // Pre-age the code.
+        Code* stub = Code::GetPreAgedCodeAgeStub(isolate());
+        __ add(r0, pc, Operand(-8));
+        __ ldr(pc, MemOperand(pc, -4));
+        __ dd(reinterpret_cast<uint32_t>(stub->instruction_start()));
+      } else {
+        __ stm(db_w, sp, r1.bit() | cp.bit() | fp.bit() | lr.bit());
+        __ nop(ip.code());
+        // Adjust FP to point to saved FP.
+        __ add(fp, sp, Operand(2 * kPointerSize));
+      }
     }
     frame_is_built_ = true;
     info_->AddNoFrameRange(0, masm_->pc_offset());