Introduce new API for detecting when the embedder is in foreground/background.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 7349 matching lines @@
   }
 }
 
 
 int Isolate::ContextDisposedNotification(bool dependant_context) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   return isolate->heap()->NotifyContextDisposed(dependant_context);
 }
 
 
+void Isolate::IsolateInForegroundNotification() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->heap()->SetOptimizeForLatency();
+}
+
+
+void Isolate::IsolateInBackgroundNotification() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->heap()->SetOptimizeForMemoryUsage();
+}
+
+
 void Isolate::SetJitCodeEventHandler(JitCodeEventOptions options,
                                      JitCodeEventHandler event_handler) {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
   // Ensure that logging is initialized for our isolate.
   isolate->InitializeLoggingAndCounters();
   isolate->logger()->SetCodeEventHandler(options, event_handler);
 }
 
 
 void Isolate::SetStackLimit(uintptr_t stack_limit) {
@@ skipping 982 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8