NotForReview: Expose the global memory budget (v8 side)

include/v8-platform.h

 // Copyright 2013 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.
 
 #ifndef V8_V8_PLATFORM_H_
 #define V8_V8_PLATFORM_H_
 
 #include <stddef.h>
 #include <stdint.h>
 #include <memory>
@@ skipping 194 matching lines @@
     virtual ~TraceStateObserver() = default;
     virtual void OnTraceEnabled() = 0;
     virtual void OnTraceDisabled() = 0;
   };
 
   /** Adds tracing state change observer. */
   virtual void AddTraceStateObserver(TraceStateObserver*) {}
 
   /** Removes tracing state change observer. */
   virtual void RemoveTraceStateObserver(TraceStateObserver*) {}
+
+  /**
+   * Returns true if the system-wide available free memory (referred to as the
+   * global memory budget) can be obtained via GetGlobalMemoryBudget().
+   */
+  virtual bool IsGlobalMemoryBudgetAvailable() { return false; }
+
+  /**
+   * Returns the global memory budget. A nagative value can be returned when
+   * the global memory budget is unknown or the system is under high memory
+   * pressure.
+   */
+  virtual int64_t GetGlobalMemoryBudget() { return -1; }
+
+  /**
+   * TODO(bashi): Tentative. Set an interval to update the global memory budget.
+   */
+  virtual void SetGlobalMemoryBudgetUpdateInterval(uint32_t interval_ms) {}
 };
 
 }  // namespace v8
 
 #endif  // V8_V8_PLATFORM_H_