Use conservative hash table capacity growth during entire snapshotting.

We want to use the conservative growth strategy during
- isolate initialization
- bootstrapping a context

But not when
- not creating a snapshot
- running additional code for custom snapshot.

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/1155823003

Cr-Commit-Position: refs/heads/master@{#28586}

src/api.cc

@@ -347,12 +347,14 @@ StartupData V8::CreateSnapshotDataBlob(const char* custom_source) {
     base::ElapsedTimer timer;
     timer.Start();
     Isolate::Scope isolate_scope(isolate);
+    internal_isolate->set_creating_default_snapshot(true);
     internal_isolate->Init(NULL);
     Persistent<Context> context;
     i::Snapshot::Metadata metadata;
     {
       HandleScope handle_scope(isolate);
       Handle<Context> new_context = Context::New(isolate);
+      internal_isolate->set_creating_default_snapshot(false);
       context.Reset(isolate, new_context);
       if (custom_source != NULL) {
         metadata.set_embeds_script(true);

src/isolate.h

@@ -378,6 +378,7 @@ typedef List<HeapObject*> DebugObjectCache;
   V(uint32_t, per_isolate_assert_data, 0xFFFFFFFFu)                            \
   V(PromiseRejectCallback, promise_reject_callback, NULL)                      \
   V(const v8::StartupData*, snapshot_blob, NULL)                               \
+  V(bool, creating_default_snapshot, false)                                    \
   ISOLATE_INIT_SIMULATOR_LIST(V)
 
 #define THREAD_LOCAL_TOP_ACCESSOR(type, name)                        \

src/objects.cc

@@ -14728,10 +14728,10 @@ Handle<Derived> HashTable<Derived, Shape, Key>::New(
     PretenureFlag pretenure) {
   DCHECK(0 <= at_least_space_for);
   DCHECK(!capacity_option || base::bits::IsPowerOfTwo32(at_least_space_for));
-  int capacity =
-      (capacity_option == USE_CUSTOM_MINIMUM_CAPACITY)
+
+  int capacity = (capacity_option == USE_CUSTOM_MINIMUM_CAPACITY)
                      ? at_least_space_for
-          : isolate->serializer_enabled() && isolate->bootstrapper()->IsActive()
+                     : isolate->creating_default_snapshot()
                            ? ComputeCapacityForSerialization(at_least_space_for)
                            : ComputeCapacity(at_least_space_for);
   if (capacity > HashTable::kMaxCapacity) {