Use a dictionary-mode code cache on the map rather than a dual system.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 14133b39b0d3df321b6b9939d1af96fd2fd0341d..e593898e423ff2d9d857c5450fd063ccd19577e4 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -283,7 +283,6 @@ class CodeStub BASE_EMBEDDED {
 
   virtual InlineCacheState GetICState() const { return UNINITIALIZED; }
   virtual ExtraICState GetExtraICState() const { return kNoExtraICState; }
-  virtual Code::StubType GetStubType() const { return Code::NORMAL; }
 
   Code::Flags GetCodeFlags() const;
 
@@ -578,8 +577,6 @@ class TurboFanCodeStub : public CodeStub {
     return GetCallInterfaceDescriptor().GetStackParameterCount();
   }
 
-  Code::StubType GetStubType() const override { return Code::FAST; }
-
  protected:
   explicit TurboFanCodeStub(Isolate* isolate) : CodeStub(isolate) {}
 
@@ -1271,7 +1268,6 @@ class LoadIndexedStringStub : public PlatformCodeStub {
       : PlatformCodeStub(isolate) {}
 
   Code::Kind GetCodeKind() const override { return Code::HANDLER; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
   DEFINE_CALL_INTERFACE_DESCRIPTOR(Load);
   DEFINE_PLATFORM_CODE_STUB(LoadIndexedString, PlatformCodeStub);
@@ -1311,7 +1307,6 @@ class LoadFieldStub: public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::LOAD_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   class LoadFieldByIndexBits : public BitField<int, 0, 13> {};
@@ -1337,7 +1332,6 @@ class ArrayBufferViewLoadFieldStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::LOAD_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   class ArrayBufferViewLoadFieldByIndexBits : public BitField<int, 0, 13> {};
@@ -1353,7 +1347,6 @@ class KeyedLoadSloppyArgumentsStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::KEYED_LOAD_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   DEFINE_HANDLER_CODE_STUB(KeyedLoadSloppyArguments, HandlerStub);
@@ -1372,7 +1365,6 @@ class KeyedStoreSloppyArgumentsStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::KEYED_STORE_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   DEFINE_HANDLER_CODE_STUB(KeyedStoreSloppyArguments, HandlerStub);
@@ -1392,7 +1384,6 @@ class LoadConstantStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::LOAD_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   class ConstantIndexBits : public BitField<int, 0, kSubMinorKeyBits> {};
@@ -1424,7 +1415,6 @@ class StoreFieldStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::STORE_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   class StoreFieldByIndexBits : public BitField<int, 0, 13> {};
@@ -1534,7 +1524,6 @@ class StoreTransitionStub : public HandlerStub {
 
  protected:
   Code::Kind kind() const override { return Code::STORE_IC; }
-  Code::StubType GetStubType() const override { return Code::FAST; }
 
  private:
   class StoreFieldByIndexBits : public BitField<int, 0, 13> {};
@@ -2488,8 +2477,6 @@ class ScriptContextFieldStub : public HandlerStub {
   class SlotIndexBits
       : public BitField<int, kContextIndexBits, kSlotIndexBits> {};
 
-  Code::StubType GetStubType() const override { return Code::FAST; }
-
   DEFINE_CODE_STUB_BASE(ScriptContextFieldStub, HandlerStub);
 };