Add UMA metrics for desktop memory pressure notifications.

base/memory/memory_pressure_monitor_mac.cc

Index: base/memory/memory_pressure_monitor_mac.cc
diff --git a/base/memory/memory_pressure_monitor_mac.cc b/base/memory/memory_pressure_monitor_mac.cc
index 9ca520e8f8a0df2d9e898662ede6503bd4d2c829..14eb1d39793656060cedb33916f99b2897fda7b0 100644
--- a/base/memory/memory_pressure_monitor_mac.cc
+++ b/base/memory/memory_pressure_monitor_mac.cc
@@ -104,7 +104,8 @@ int MemoryPressureMonitor::GetMacMemoryPressureLevel() {
   size_t length = sizeof(int);
   sysctlbyname("kern.memorystatus_vm_pressure_level",
                &mac_memory_pressure_level, &length, nullptr, 0);
-
+  printf("kern memory pressure = %d\n", mac_memory_pressure_level);
+  
   return mac_memory_pressure_level;
 }
 
@@ -112,6 +113,7 @@ void MemoryPressureMonitor::UpdatePressureLevel() {
   // Get the current macOS pressure level and convert to the corresponding
   // Chrome pressure level.
   int mac_memory_pressure_level = GetMacMemoryPressureLevel();
+printf("updating pressure level to %d\n", mac_memory_pressure_level);
   MemoryPressureListener::MemoryPressureLevel new_pressure_level =
       MemoryPressureLevelForMacMemoryPressureLevel(mac_memory_pressure_level);
 
@@ -162,7 +164,12 @@ int MemoryPressureMonitor::GetSecondsPerUMATick() {
 
 MemoryPressureListener::MemoryPressureLevel
 MemoryPressureMonitor::GetCurrentPressureLevel() {
-  return last_pressure_level_;
+  MemoryPressureListener::MemoryPressureLevel level = MemoryPressureLevelForMacMemoryPressureLevel(GetMacMemoryPressureLevel());
+printf(" GetCurrentPressureLevel = %d\n", level);
+  return level;
+
+
+  //return last_pressure_level_;
 }
 
 void MemoryPressureMonitor::OnMemoryPressureChanged(
@@ -170,6 +177,7 @@ void MemoryPressureMonitor::OnMemoryPressureChanged(
     const MemoryPressureMonitor::DispatchCallback& dispatch_callback) {
   // Get the Chrome-equvialent memory pressure level.
   int mac_memory_pressure_level = dispatch_source_get_data(event_source);
+printf("OnChanged to %d\n", mac_memory_pressure_level);
   MemoryPressureListener::MemoryPressureLevel memory_pressure_level =
       MemoryPressureLevelForMacMemoryPressureLevel(mac_memory_pressure_level);