Patch RecordWriteStub after adding it to the stub cache not during generation.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 9432304a5af6c338e43aad9c7f38c856c6e092b7..bb365c880d291b2f220f7620740ced780acfcade 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -5182,18 +5182,10 @@ void RecordWriteStub::Generate(MacroAssembler* masm) {
   __ bind(&skip_to_incremental_compacting);
   GenerateIncremental(masm, INCREMENTAL_COMPACTION);
 
-  // TODO(1545) ensure that GC can't happen after stub was generated by before
-  // it was added to a stub cache.
-  IncrementalMarking* marking = masm->isolate()->heap()->incremental_marking();
-  if (!marking->IsMarking() || marking->IsCompacting()) {
-    ASSERT(masm->byte_at(0) == kTwoByteJumpInstruction);
-    masm->set_byte_at(0, kTwoByteNopInstruction);
-  }
-
-  if (!marking->IsMarking()) {
-    ASSERT(masm->byte_at(2) == kFiveByteJumpInstruction);
-    masm->set_byte_at(2, kFiveByteNopInstruction);
-  }
+  // Initial mode of the stub is expected to be STORE_BUFFER_ONLY.
+  // Will be checked in IncrementalMarking::ActivateGeneratedStub.
+  masm->set_byte_at(0, kTwoByteNopInstruction);
+  masm->set_byte_at(2, kFiveByteNopInstruction);
 }