Add architecture for simulating memory pressure notifications in all processes

content/common/memory_messages.h

Index: content/common/memory_messages.h
diff --git a/content/common/memory_messages.h b/content/common/memory_messages.h
index a81eaf871491fb2e8bbf1af62e69dcaca94afd3d..f013b68d77338295bbc7735c0f9a3ad19414e4a2 100644
--- a/content/common/memory_messages.h
+++ b/content/common/memory_messages.h
@@ -8,6 +8,7 @@
 
 // Multiply-included message header, no traditional include guard.
 
+#include "base/memory/memory_pressure_listener.h"
 #include "ipc/ipc_message_macros.h"
 #include "content/common/content_export.h"
 
@@ -16,7 +17,18 @@
 
 #define IPC_MESSAGE_START MemoryMsgStart
 
-// Sent to all child processes to enable/disable suppressing memory
+using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;
+
+IPC_ENUM_TRAITS_VALIDATE(
+    MemoryPressureLevel,
+    (value == MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_MODERATE ||
+     value == MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_CRITICAL))
+
+// Sent to all child processes to enable/disable suppressing memory pressure
 // notifications.
 IPC_MESSAGE_CONTROL1(MemoryMsg_SetPressureNotificationsSuppressed,
                      bool /* suppressed */)
+
+// Sent to all child processes to simulate a memory pressure notification.
+IPC_MESSAGE_CONTROL1(MemoryMsg_SimulatePressureNotification,
+                     MemoryPressureLevel /* level */)