LevelDB storage for data reduction proxy to store data usage stats.

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 08573decfd4e845caa88dd657f7db47337215fa9..1dc44def446daea8ee55cdece1d7efdd44d943c8 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4787,6 +4787,12 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="DataReductionProxy.LevelDBOpenStatus"
+    enum="DataReductionProxyStoreStatus">
+  <owner>kundaji@chromium.org</owner>
+  <summary>Status of calling Open() on Data Reduction Proxy LevelDB.</summary>
+</histogram>
+
 <histogram name="DataReductionProxy.LoFi.ImplicitOptOutAction"
     enum="DataReductionProxyLoFiImplicitOptOutAction">
   <owner>bengr@chromium.org</owner>
@@ -52185,6 +52191,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="2" label="Proxy available and enabled"/>
 </enum>
 
+<enum name="DataReductionProxyStoreStatus" type="int">
+  <int value="0" label="OK"/>
+  <int value="1" label="NOT_FOUND"/>
+  <int value="2" label="CORRUPTED"/>
+  <int value="3" label="IO_ERROR"/>
+  <int value="4" label="MISC_ERROR"/>
+</enum>
+
 <enum name="DataReductionProxyUIAction" type="int">
   <int value="0" label="Enabled directly from the promo"/>
   <int value="1" label="Enabled then disabled from promo (iOS-only)"/>