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(level,
+                                                     Locker::IsLocked(this));

[jochen (gone - plz use gerrit), 2016/03/18 15:29:12]

as explained offline, Locker::IsLocked() always returns false in blink (as it
doesn't use lockers).

in general, we can't know whether the "main" thread is running JS currently
(without races), so I'd recommend to set the interrupt flag and internally
schedule a task using PostTaskOnForegroundThread() to make sure that the
interrupt flag actually gets honored.

[ulan, 2016/03/18 16:10:00]

Done.

+}
 
 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