Add memory pressure notification API

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 7568 matching lines @@
   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::MemoryPressureNotification(MemoryPressureLevel level) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->heap()->MemoryPressureNotification(
+      static_cast<i::MemoryPressureLevel>(level), Locker::IsLocked(this));

[jochen (gone - plz use gerrit), 2016/03/17 19:33:39]

IsLocked() should never be true in blink, right?

[ulan, 2016/03/18 12:49:40]

If V8 is not executing JS code and there is memory pressure event in chrome,
then it would be optimal to enter the isolate and then call the function. That
way we can do GC immediately.  Otherwise, the notification will have no effect
until V8 starts running.

+}
 
 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);
 }
 
 
@@ skipping 1086 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