Define histograms for Android-specific memory conditions in the field.

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 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.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 919 matching lines @@
 <histogram name="Media.DetectedVideoCodec" enum="FFmpegCodecs">
   <summary>Video codec used in HTML5 media.</summary>
 </histogram>
 
 <histogram name="Media.VAVDAH264.DecoderFailure" enum="VAVDAH264DecoderFailure">
   <summary>
     Error codes reported by video decode using VA-API hardware video decoder.
   </summary>
 </histogram>
 
+<histogram name="MemoryAndroid.DeviceMemoryClass">
+  <summary>
+    Value of getMemoryClass() recorded once upon startup. This is an integer,
+    device-specific constant correlated with the amount of memory available on
+    Android device.
+  </summary>
+</histogram>
+
+<histogram name="MemoryAndroid.EvictionReason" enum="AndroidEvictionReason">
+  <summary>
+    Reasons behind evictions of individual tabs, recorded upon each tab
+    eviction.
+  </summary>
+</histogram>
+
+<histogram name="MemoryAndroid.LowMemoryLoadedTabCount">
+  <summary>
+    Number of loaded (memory-resident) tabs when LowMemory notification is
+    delivered.
+  </summary>
+</histogram>
+
+<histogram name="MemoryAndroid.LowMemoryTimeBetween" units="milliseconds">
+  <summary>
+    Time between two consecutive LowMemory notification in one foreground
+    session.
+  </summary>
+</histogram>
+
+<histogram name="MemoryAndroid.NotificationBackground"
+    enum="AndroidMemoryNotificationBackground">
+  <summary>
+    Memory notifications delivered through system callbacks to Chrome while in
+    the background.
+  </summary>
+</histogram>
+
+<histogram name="MemoryAndroid.NotificationForeground"
+    enum="AndroidMemoryNotificationForeground">
+  <summary>
+    Memory notifications delivered through system callbacks to Chrome while in
+    the foreground - we count LowMemory notification vs particular levels of
+    TrimMemory foreground notification.
+  </summary>
+</histogram>
+
 <histogram name="Navigation.MainFrameScheme" enum="NavigationScheme">
   <summary>The scheme of the URL for each main-frame navigation.</summary>
 </histogram>
 
 <histogram name="Net.AsyncResourceHandler_PendingDataCount">
   <summary>
     The count of unacknowledged ResourceMsg_DataReceived messages.  This message
     is sent once per chunk of data read from the network.
   </summary>
 </histogram>
@@ skipping 5025 matching lines @@
 
 <!-- Enum types -->
 
 <enums>
 
 <enum name="Abandoned" type="int">
   <int value="0" label="Finished"/>
   <int value="1" label="Abandoned"/>
 </enum>
 
+<enum name="AndroidEvictionReason" type="int">
+  <int value="0" label="TabUnusedTooLong"/>
+  <int value="1" label="TabUnusedInSession"/>
+  <int value="2" label="LimitOfActiveTabs"/>
+  <int value="3" label="EvictNTabs"/>
+  <int value="4" label="EvictAll"/>
+</enum>
+
+<enum name="AndroidMemoryNotificationBackground" type="int">
+  <int value="0" label="TrimMemoryUiHidden"/>
+  <int value="1" label="TrimMemoryBackground"/>
+  <int value="2" label="TrimMemoryModerate"/>
+  <int value="3" label="TrimMemoryComplete"/>
+</enum>
+
+<enum name="AndroidMemoryNotificationForeground" type="int">
+  <int value="0" label="TrimMemoryRunningModerate"/>
+  <int value="1" label="TrimMemoryRunningLow"/>
+  <int value="2" label="TrimMemoryRunningCritical"/>
+  <int value="3" label="LowMemory"/>
+</enum>
+
 <enum name="AudioRendererEvents" type="int">
   <int value="0" label="Initialized"/>
   <int value="1" label="Runtime error"/>
 </enum>
 
 <enum name="AutocheckoutBubble" type="int">
   <int value="0" label="Created"/>
   <int value="1" label="Accepted"/>
   <int value="2" label="Dismissed"/>
   <int value="3" label="Ignored"/>
@@ skipping 4358 matching lines @@
 <fieldtrial name="SSLResumption">
   <group name="Resume_Handshake" label="Session Resumption"/>
   <group name="Full_Handshake" label="Full"/>
   <affected-histogram name="Net.SSL_Connection_Latency"/>
   <affected-histogram name="Net.SSL_Connection_Latency_Google"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>