Remove unused metric from memory_pressure component.

components/memory_pressure/memory_pressure_stats_collector.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/memory_pressure/memory_pressure_stats_collector.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 32 matching lines @@
     case UMA_MEMORY_PRESSURE_LEVEL_CRITICAL:
       return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
     case UMA_MEMORY_PRESSURE_LEVEL_COUNT:
       NOTREACHED();
       break;
   }
   NOTREACHED();
   return MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
 }
 
-// Converts a pressure state change to an UMA enumeration value.
-MemoryPressureLevelChangeUMA MemoryPressureLevelChangeToUmaEnumValue(
-    MemoryPressureLevel old_level,
-    MemoryPressureLevel new_level) {
-  switch (old_level) {
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE: {
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_NONE_TO_MODERATE;
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_NONE_TO_CRITICAL;
-      break;  // Should never happen; handled by the NOTREACHED below.
-    }
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE: {
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_MODERATE_TO_NONE;
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_MODERATE_TO_CRITICAL;
-      break;  // Should never happen; handled by the NOTREACHED below.
-    }
-    case MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL: {
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_CRITICAL_TO_MODERATE;
-      if (new_level == MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE)
-        return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_CRITICAL_TO_MODERATE;
-      break;  // Should never happen; handled by the NOTREACHED below.
-    }
-  }
-  NOTREACHED();
-  return UMA_MEMORY_PRESSURE_LEVEL_CHANGE_NONE_TO_MODERATE;
-}
-
 }  // namespace
 
 MemoryPressureStatsCollector::MemoryPressureStatsCollector(
     base::TickClock* tick_clock)
     : tick_clock_(tick_clock),
       last_pressure_level_(MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE) {
 }
 
 void MemoryPressureStatsCollector::UpdateStatistics(
     MemoryPressureLevel current_pressure_level) {
@@ skipping 48 matching lines @@
       base::LinearHistogram::FactoryGet(
           "Memory.PressureLevel", 1, UMA_MEMORY_PRESSURE_LEVEL_COUNT,
           UMA_MEMORY_PRESSURE_LEVEL_COUNT + 1,
           base::HistogramBase::kUmaTargetedHistogramFlag));
 }
 
 // static
 void MemoryPressureStatsCollector::ReportLevelChange(
     MemoryPressureLevel old_pressure_level,
     MemoryPressureLevel new_pressure_level) {
-  UMA_HISTOGRAM_ENUMERATION("Memory.PressureLevelChange",
-                            MemoryPressureLevelChangeToUmaEnumValue(
-                                old_pressure_level, new_pressure_level),
-                            UMA_MEMORY_PRESSURE_LEVEL_CHANGE_COUNT);
+  // TODO(chrisha): Report Memory.PressureLevelChange when this code is in use.
 }
 
 }  // namespace memory_pressure