NotForReview: Expose the global memory budget (v8 side)

include/v8-platform.h

Index: include/v8-platform.h
diff --git a/include/v8-platform.h b/include/v8-platform.h
index e11567488b6a3ca45780d52d11d6d1b3696b44ba..41d2b40fbb2b23f047f9de41898eb00c99c4c10b 100644
--- a/include/v8-platform.h
+++ b/include/v8-platform.h
@@ -212,6 +212,24 @@ class Platform {
 
   /** 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