Add MC to test disabling React Native invalidation under memory pressure

Summary: Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D35732504

fbshipit-source-id: d81d6ddefc98d1e73be697c3eef8a2c90104658c

React/Base/RCTConstants.h

@@ -21,3 +21,15 @@ RCT_EXTERN void RCTExperimentSetPreemptiveViewAllocationDisabled(BOOL value);
  */
 RCT_EXTERN BOOL RCTGetDispatchW3CPointerEvents(void);
 RCT_EXTERN void RCTSetDispatchW3CPointerEvents(BOOL value);
+
+/*
+ * Memory Pressure Unloading
+ */
+RCT_EXTERN BOOL RCTGetDisableBridgeMemoryPressureUnload(void);
+RCT_EXTERN void RCTSetDisableBridgeMemoryPressureUnload(BOOL value);
+
+/*
+ * Memory Pressure Unloading Level
+ */
+RCT_EXTERN BOOL RCTGetMemoryPressureUnloadLevel(void);
+RCT_EXTERN void RCTSetMemoryPressureUnloadLevel(int value);

React/Base/RCTConstants.m

@@ -39,3 +39,34 @@ void RCTSetDispatchW3CPointerEvents(BOOL value)
 {
   RCTDispatchW3CPointerEvents = value;
 }
+
+/*
+ * Memory Pressure Unloading
+ */
+static BOOL RCTDisableBridgeMemoryPressureUnload = NO;
+
+BOOL RCTGetDisableBridgeMemoryPressureUnload()
+{
+  return RCTDisableBridgeMemoryPressureUnload;
+}
+
+void RCTSetDisableBridgeMemoryPressureUnload(BOOL value)
+{
+  RCTDisableBridgeMemoryPressureUnload = value;
+}
+
+/*
+ * Memory Pressure Unloading Level for experimentation only.
+ * Default is 15, which is TRIM_MEMORY_RUNNING_CRITICAL.
+ */
+static int RCTMemoryPressureUnloadLevel = 15;
+
+BOOL RCTGetMemoryPressureUnloadLevel()
+{
+  return RCTMemoryPressureUnloadLevel;
+}
+
+void RCTSetMemoryPressureUnloadLevel(int value)
+{
+  RCTMemoryPressureUnloadLevel = value;
+}

React/CxxBridge/RCTCxxBridge.mm

@@ -359,7 +359,8 @@ struct RCTInstanceCallback : public InstanceCallback {
   // in case if some other tread resets it.
   auto reactInstance = _reactInstance;
   if (reactInstance) {
-    reactInstance->handleMemoryPressure(15 /* TRIM_MEMORY_RUNNING_CRITICAL */);
+    int unloadLevel = RCTGetMemoryPressureUnloadLevel();
+    reactInstance->handleMemoryPressure(unloadLevel);
   }
 }