Revert "Flush ICache on startup deserialization after marking memory executable"

This reverts commit 05bcb12e.

Reason for revert: Causes isolate startup regressions (https://crbug.com/845508)

Original change's description:
> Flush ICache on startup deserialization after marking memory executable
>
> Tentative fix for Android invoke crashers with write protection code
> enabled.
>
> Bug: chromium:842862
> Change-Id: If238b25b239b50c597f3745aa683f564a717434f
> Reviewed-on: https://chromium-review.googlesource.com/1061513
> Reviewed-by: Jakob Gruber <jgruber@chromium.org>
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#53209}

TBR=mstarzinger@chromium.org,cbruni@chromium.org,jgruber@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:842862, chromium:845508, chromium:845877
Change-Id: Iff002e1ac75aca48c696053dddf1b413f372629e
Reviewed-on: https://chromium-review.googlesource.com/1068048
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53305}

src/isolate.cc

@@ -3085,10 +3085,6 @@ bool Isolate::Init(StartupDeserializer* des) {
 
     heap_.NotifyDeserializationComplete();
   }
-  // Flush the instruction cache for the entire code-space. Must happen after
-  // builtins deserialization and setting the memory executable again.
-  if (!create_heap_objects) des->FlushICacheForNewIsolate();
-
   delete setup_delegate_;
   setup_delegate_ = nullptr;
 

src/snapshot/startup-deserializer.cc

@@ -45,6 +45,10 @@ void StartupDeserializer::DeserializeInto(Isolate* isolate) {
     // Deserialize eager builtins from the builtin snapshot. Note that deferred
     // objects must have been deserialized prior to this.
     builtin_deserializer.DeserializeEagerBuiltinsAndHandlers();
+
+    // Flush the instruction cache for the entire code-space. Must happen after
+    // builtins deserialization.
+    FlushICacheForNewIsolate();
   }
 
   isolate->heap()->set_native_contexts_list(isolate->heap()->undefined_value());

src/snapshot/startup-deserializer.h

@@ -21,9 +21,8 @@ class StartupDeserializer final : public Deserializer<> {
   // Deserialize the snapshot into an empty heap.
   void DeserializeInto(Isolate* isolate);
 
-  void FlushICacheForNewIsolate();
-
  private:
+  void FlushICacheForNewIsolate();
   void PrintDisassembledCodeObjects();
 
   // Rehash after deserializing an isolate.