[snapshot] add timers to no-snapshot code path.

This is to compare the the no-snapshot build to the
snapshot build when creating an isolate or context.

R=jgruber@chromium.org

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I503cde560b7897b945b3f9d2b445d0abcbfb5b60
Reviewed-on: https://chromium-review.googlesource.com/571744Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46674}

src/api.cc

@@ -8470,7 +8470,13 @@ Isolate* IsolateNewImpl(internal::Isolate* isolate,
   // TODO(jochen): Once we got rid of Isolate::Current(), we can remove this.
   Isolate::Scope isolate_scope(v8_isolate);
   if (params.entry_hook || !i::Snapshot::Initialize(isolate)) {
+    base::ElapsedTimer timer;
+    if (i::FLAG_profile_deserialization) timer.Start();
     isolate->Init(NULL);
+    if (i::FLAG_profile_deserialization) {
+      double ms = timer.Elapsed().InMillisecondsF();
+      i::PrintF("[Initializing isolate from scratch took %0.3f ms]\n", ms);
+    }
   }
   return v8_isolate;
 }

src/bootstrapper.cc

@@ -5154,6 +5154,8 @@ Genesis::Genesis(
     }
     DCHECK(!global_proxy->IsDetachedFrom(native_context()->global_object()));
   } else {
+    base::ElapsedTimer timer;
+    if (FLAG_profile_deserialization) timer.Start();
     DCHECK_EQ(0u, context_snapshot_index);
     // We get here if there was no context snapshot.
     CreateRoots();
@@ -5174,6 +5176,11 @@ Genesis::Genesis(
     if (!ConfigureGlobalObjects(global_proxy_template)) return;
 
     isolate->counters()->contexts_created_from_scratch()->Increment();
+
+    if (FLAG_profile_deserialization) {
+      double ms = timer.Elapsed().InMillisecondsF();
+      i::PrintF("[Initializing context from scratch took %0.3f ms]\n", ms);
+    }
   }
 
   // Install experimental natives. Do not include them into the