deps: cherry-pick 09db540,686558d from V8 upstream

Original commit messages:
v8/v8@09db540
  Reland of Rehash and clear deleted entries in weak collections during GC

  BUG=v8:4909
  R=hpayer@chromium.org,ulan@chromium.org
  LOG=n

  Review URL: https://codereview.chromium.org/1890123002

  Cr-Commit-Position: refs/heads/master@{#35538}

v8/v8@686558d
  Fix comment about when we rehash ObjectHashTables before growing them

  R=ulan@chromium.org
  BUG=

  Review-Url: https://codereview.chromium.org/1918403003
  Cr-Commit-Position: refs/heads/master@{#35853}

Refs: https://crbug.com/v8/4909
Refs: #6180
Refs: #7689
Refs: #6398
Fixes: #14228

PR-URL: #14829
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

deps/v8/include/v8-version.h

@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 4
 #define V8_MINOR_VERSION 5
 #define V8_BUILD_NUMBER 103
-#define V8_PATCH_LEVEL 48
+#define V8_PATCH_LEVEL 49
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)

deps/v8/src/objects.cc

@@ -13744,6 +13744,16 @@ void HashTable<Derived, Shape, Key>::Rehash(Key key) {
       }
     }
   }
+  // Wipe deleted entries.
+  Heap* heap = GetHeap();
+  Object* the_hole = heap->the_hole_value();
+  Object* undefined = heap->undefined_value();
+  for (uint32_t current = 0; current < capacity; current++) {
+    if (get(EntryToIndex(current)) == the_hole) {
+      set(EntryToIndex(current), undefined);
+    }
+  }
+  SetNumberOfDeletedElements(0);
 }
 
 
@@ -15198,6 +15208,11 @@ Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,
     return table;
   }
 
+  // Rehash if more than 33% of the entries are deleted entries.
+  // TODO(jochen): Consider to shrink the fixed array in place.
+  if ((table->NumberOfDeletedElements() << 1) > table->NumberOfElements()) {
+    table->Rehash(isolate->factory()->undefined_value());
+  }
   // If we're out of luck, we didn't get a GC recently, and so rehashing
   // isn't enough to avoid a crash.
   if (!table->HasSufficientCapacityToAdd(1)) {