Remove unused metric from memory_pressurecomponent.

BUG=643523
TBR=georgesak@chromium.org

Review-Url: https://codereview.chromium.org/2317083002
Cr-Commit-Position: refs/heads/master@{#417050}

components/memory_pressure/memory_pressure_stats_collector.cc

@@ -50,37 +50,6 @@ MemoryPressureLevel MemoryPressureLevelFromUmaEnumValue(
   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(
@@ -149,10 +118,7 @@ void MemoryPressureStatsCollector::ReportCumulativeTime(
 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

components/memory_pressure/memory_pressure_stats_collector_unittest.cc

@@ -14,7 +14,6 @@ namespace {
 
 // Histogram names.
 const char kPressureLevel[] = "Memory.PressureLevel";
-const char kPressureLevelChange[] = "Memory.PressureLevelChange";
 
 }  // namespace
 
@@ -81,7 +80,6 @@ TEST_F(MemoryPressureStatsCollectorTest, EndToEnd) {
   // Upon construction no statistics should yet have been reported.
   ExpectAccumulated(0, 0, 0);
   ExpectReported(0, 0, 0);
-  histograms_.ExpectTotalCount(kPressureLevelChange, 0);
 
   // A first call should not invoke any reporting functions, but it should
   // modify member variables.
@@ -93,7 +91,6 @@ TEST_F(MemoryPressureStatsCollectorTest, EndToEnd) {
   EXPECT_EQ(tick_clock_.NowTicks(), collector_.last_update_time());
   ExpectAccumulated(0, 0, 0);
   ExpectReported(0, 0, 0);
-  histograms_.ExpectTotalCount(kPressureLevelChange, 0);
 
   // A subsequent call with the same pressure level should increment the
   // cumulative time but not make a report, as less than one second of time
@@ -106,7 +103,6 @@ TEST_F(MemoryPressureStatsCollectorTest, EndToEnd) {
   EXPECT_EQ(tick_clock_.NowTicks(), collector_.last_update_time());
   ExpectAccumulated(500, 0, 0);
   ExpectReported(0, 0, 0);
-  histograms_.ExpectTotalCount(kPressureLevelChange, 0);
 
   // Yet another call and this time a report should be made, as one second
   // of time has been accumulated. 500ms should remain unreported.
@@ -118,7 +114,6 @@ TEST_F(MemoryPressureStatsCollectorTest, EndToEnd) {
   EXPECT_EQ(tick_clock_.NowTicks(), collector_.last_update_time());
   ExpectAccumulated(500, 0, 0);
   ExpectReported(1, 0, 0);
-  histograms_.ExpectTotalCount(kPressureLevelChange, 0);
 
   // A subsequent call with a different pressure level should increment the
   // cumulative time and make several reports.
@@ -130,10 +125,6 @@ TEST_F(MemoryPressureStatsCollectorTest, EndToEnd) {
   EXPECT_EQ(tick_clock_.NowTicks(), collector_.last_update_time());
   ExpectAccumulated(500, 250, 0);
   ExpectReported(1, 2, 0);
-  histograms_.ExpectBucketCount(
-      kPressureLevelChange, UMA_MEMORY_PRESSURE_LEVEL_CHANGE_NONE_TO_MODERATE,
-      1);
-  histograms_.ExpectTotalCount(kPressureLevelChange, 1);
 }
 
 }  // namespace memory_pressure