tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index f9b9ebdebef0cf7a01fe6844262ce007491af345..23fecfac22b6b02570d97d3bdf3ebd7d2cafb67b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3801,8 +3801,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
-<histogram name="ChromeOS.MemoryPressureLevel"
-    enum="ChromeOSMemoryPressureLevel">
+<histogram name="ChromeOS.MemoryPressureLevel" enum="MemoryPressureLevel">

[rkaplow, 2015/09/03 17:22:36]

similar to other comment - we're changing this, but won't the old logic still be
writing to ChromeOS.MemoryPressureLevel

[chrisha, 2015/09/03 20:00:45]

The old logic will continue writing here until the switch to the component
implementation. At the moment of the switch, this histogram will not longer be
written to, and will be deprecated.

(I took the liberty of cleaning up the identical enum that the two histograms
were referring to.)

   <owner>xdai@chromium.org</owner>
   <summary>
     The memory pressure level in ChromeOS, which is recorded periodically (once
@@ -18097,12 +18096,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 <histogram name="Memory.PressureLevel" enum="MemoryPressureLevel">
   <owner>chrisha@chromium.org</owner>
   <summary>
-    The memory pressure level, which is recorded periodically (once per second).
-    This is used to show the relative time that systems spend in each of the
-    memory pressure states.
+    The memory pressure level, which is recorded periodically. This shows the
+    cumulative number of seconds that systems spend in each of the memory
+    pressure states.
   </summary>
 </histogram>
 
+<histogram name="Memory.PressureLevelChanges" enum="MemoryPressureLevelChanges">
+  <owner>chrisha@chromium.org</owner>
+  <summary>The number of pressure level state changes.</summary>
+</histogram>
+
 <histogram name="Memory.ProcessCount">
   <owner>hajimehoshi@chromium.org</owner>
   <owner>kenjibaheux@google.com</owner>
@@ -54084,12 +54088,6 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Periodic"/>
 </enum>
 
-<enum name="ChromeOSMemoryPressureLevel" type="int">
-  <int value="0" label="No memory pressure"/>
-  <int value="1" label="Medium memory pressure"/>
-  <int value="2" label="High memory pressure"/>
-</enum>
-
 <enum name="ChromeOSPlatformVerificationExpiryStatus" type="int">
   <summary>
     Possible results of a platform verification expiry check. See
@@ -65067,6 +65065,15 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="2" label="Critical memory pressure"/>
 </enum>
 
+<enum name="MemoryPressureLevelChanges" type="int">
+  <int value="0" label="No pressure to moderate pressure"/>
+  <int value="1" label="No pressure to critical pressure"/>
+  <int value="2" label="Moderate pressure to critical pressure"/>
+  <int value="3" label="Critical pressure to moderate pressure"/>
+  <int value="4" label="Critical pressure to no pressure"/>
+  <int value="5" label="Moderate pressure to no pressure"/>
+</enum>
+
 <enum name="MetadataReadResult" type="int">
   <int value="0" label="Success"/>
   <int value="1" label="Open failure"/>