If we can't rehash the backing store for weak sets & maps, do a last resort GC

BUG=v8:4909
R=hpayer@chromium.org

Review-Url: https://codereview.chromium.org/2129933002
Cr-Commit-Position: refs/heads/master@{#37591}

src/objects.cc

@@ -17696,6 +17696,19 @@ Handle<ObjectHashTable> ObjectHashTable::Put(Handle<ObjectHashTable> table,
   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.
+  int nof = table->NumberOfElements() + 1;
+  if (!table->HasSufficientCapacity(nof)) {
+    int capacity = ObjectHashTable::ComputeCapacity(nof * 2);
+    if (capacity > ObjectHashTable::kMaxCapacity) {
+      for (size_t i = 0; i < 2; ++i) {
+        isolate->heap()->CollectAllGarbage(
+            Heap::kFinalizeIncrementalMarkingMask, "full object hash table");
+      }
+      table->Rehash(isolate->factory()->undefined_value());
+    }
+  }
 
   // Check whether the hash table should be extended.
   table = EnsureCapacity(table, 1, key);