Reland "[runtime] Decrease StringTable shrink limit"

- Allow deserializer to add entries to the StringTable without
  causing a gc.

This is a reland of 868ed8ee

Original change's description:
> [runtime] Decrease StringTable shrink limit
>
> Given that we have not seen any regressions yet we're trying a more aggressive
> limit.
>
> Bug: chromium:818642, v8:5443
> Change-Id: Ic45001ed6c042fc31cbba0d417d5060d2de8fb3a
> Reviewed-on: https://chromium-review.googlesource.com/975126
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#52145}

Bug: chromium:818642, v8:5443
Change-Id: I051c6a79e59ec40cf87cab5bf06c4c449f8113d0
Reviewed-on: https://chromium-review.googlesource.com/975643
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52242}

src/objects.cc

@@ -17065,20 +17065,28 @@ Handle<String> StringTable::LookupKey(Isolate* isolate, StringTableKey* key) {
   table = StringTable::CautiousShrink(table);
   // Adding new string. Grow table if needed.
   table = StringTable::EnsureCapacity(table, 1);
+  isolate->heap()->SetRootStringTable(*table);
+
+  return AddKeyNoResize(isolate, key);
+}
 
+Handle<String> StringTable::AddKeyNoResize(Isolate* isolate,
+                                           StringTableKey* key) {
+  Handle<StringTable> table = isolate->factory()->string_table();
+  DCHECK(table->HasSufficientCapacityToAdd(1));
   // Create string object.
   Handle<String> string = key->AsHandle(isolate);
   // There must be no attempts to internalize strings that could throw
   // InvalidStringLength error.
   CHECK(!string.is_null());
   DCHECK(string->HasHashCode());
+  DCHECK_EQ(table->FindEntry(key), kNotFound);
 
   // Add the new string and return it along with the string table.
-  entry = table->FindInsertionEntry(key->Hash());
+  int entry = table->FindInsertionEntry(key->Hash());
   table->set(EntryToIndex(entry), *string);
   table->ElementAdded();
 
-  isolate->heap()->SetRootStringTable(*table);
   return Handle<String>::cast(string);
 }
 

src/objects/string-table.h

@@ -61,6 +61,7 @@ class StringTable : public HashTable<StringTable, StringTableShape> {
   V8_EXPORT_PRIVATE static Handle<String> LookupString(Isolate* isolate,
                                                        Handle<String> key);
   static Handle<String> LookupKey(Isolate* isolate, StringTableKey* key);
+  static Handle<String> AddKeyNoResize(Isolate* isolate, StringTableKey* key);
   static String* ForwardStringIfExists(Isolate* isolate, StringTableKey* key,
                                        String* string);
 
@@ -78,7 +79,7 @@ class StringTable : public HashTable<StringTable, StringTableShape> {
 
   DECL_CAST(StringTable)
 
-  static const int kMaxEmptyFactor = 16;
+  static const int kMaxEmptyFactor = 8;
   static const int kMinCapacity = 2048;
   static const int kMinShrinkCapacity = kMinCapacity;
 

src/snapshot/object-deserializer.cc

@@ -102,9 +102,10 @@ void ObjectDeserializer::CommitPostProcessedObjects() {
   StringTable::EnsureCapacityForDeserialization(
       isolate(), static_cast<int>(new_internalized_strings().size()));
   for (Handle<String> string : new_internalized_strings()) {
+    DisallowHeapAllocation no_gc;
     StringTableInsertionKey key(*string);
     DCHECK_NULL(StringTable::ForwardStringIfExists(isolate(), &key, *string));
-    StringTable::LookupKey(isolate(), &key);
+    StringTable::AddKeyNoResize(isolate(), &key);
   }
 
   Heap* heap = isolate()->heap();