Track UMA stats for running out of tile memory

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 b460be5edc9779b18d2df3adfe4b534b599449ac..cfb1f50f5364d17b2a2c2db96c769acf4f9c8ee6 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -32129,6 +32129,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="TileManager.ExceededMemoryBudget" enum="TileMemoryBudget">
+  <owner>reveman@chromium.org</owner>
+  <owner>vmpstr@chromium.org</owner>
+  <summary>
+    Tracks if tile memory hard limited is crossed and oom is encountered. When
+    there is no gpu memory left to assign to the tiles, at any point of time
+    TileMemoryBudget hits true, indicating a exceeded memory budget in
+    tilemanager.

[Ilya Sherman, 2014/07/11 22:40:25]

I meant that you should describe the condition that triggers logging of this
metric, regardless of which bucket is emitted to.  Here's my suggested
rewording; feel free to further refine it:

"""
Measures whether the tile manager exceeded the hard GPU memory budget (OOMed). 
Recorded each time the tile manager assigns GPU memory to tiles.
"""

[sivag, 2014/07/14 11:27:52]

Done.

+  </summary>
+</histogram>
+
 <histogram name="TimeZone.TimeZoneRequest.Event" enum="TimeZoneRequestEvent">
   <summary>Events in TimeZoneRequest.</summary>
 </histogram>
@@ -47179,6 +47190,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="9" label="No syn data + probe failed"/>
 </enum>
 
+<enum name="TileMemoryBudget" type="int">
+  <int value="0" label="With in the memory budget"/>

[Ilya Sherman, 2014/07/11 22:40:25]

nit: "With in the" -> "Within"

[sivag, 2014/07/14 11:27:52]

Done.

+  <int value="1" label="Exceeded memory budget"/>
+</enum>
+
 <enum name="TimeZoneRequestEvent" type="int">
   <int value="0" label="Request start"/>
   <int value="1" label="Response success"/>