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

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 6df77a43df3fcd0532747770913cf5fdca9d4645..d32ccf79c114f8b53bde20d01ecaf596e8e411ca 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -937,6 +937,52 @@ other types of suffix sets.
   </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>
@@ -5982,6 +6028,28 @@ other types of suffix sets.
   <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"/>