SimpleCache: histogram queuing delays and I/O portion of more ops.

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 f5f47285828c66553d647aae2c867d072cdf2777..959c9a668dfa5d6d9a7b87de2feb62db236b1d82 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -67416,6 +67416,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="SimpleCache.DiskCreateLatency" units="ms">
+  <owner>morlovich@chromium.org</owner>
+  <summary>
+    The time to access (open for creation and write initial headers) the cache
+    entry on disk.

[xunjieli, 2017/05/02 18:21:29]

If we only care about the success case, we should mention it in the summary that
this histogram is only reported on success.

[Maks Orlovich, 2017/05/02 19:49:20]

Done.

+  </summary>
+</histogram>
+
 <histogram name="SimpleCache.DiskOpenLatency" units="ms">
   <owner>rdsmith@chromium.org</owner>
   <summary>
@@ -67837,6 +67845,22 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram base="true" name="SimpleCache.QueueLatency.CreateEntry" units="ms">
+  <owner>morlovich@chromium.org</owner>
+  <summary>
+    Delay between when the I/O portion of CreateEntry is enqueued and when its
+    execution begins.
+  </summary>
+</histogram>
+
+<histogram base="true" name="SimpleCache.QueueLatency.OpenEntry" units="ms">
+  <owner>morlovich@chromium.org</owner>
+  <summary>
+    Delay between when the I/O portion of OpenEntry is enqueued and when its
+    execution begins.
+  </summary>
+</histogram>
+
 <histogram base="true" name="SimpleCache.ReadIsParallelizable"
     enum="SimpleCacheReadParallelizable">
   <owner>gavinp@chromium.org</owner>
@@ -119799,6 +119823,7 @@ from previous Chrome versions.
   <affected-histogram name="SimpleCache.CheckCRCResult"/>
   <affected-histogram name="SimpleCache.CreationToIndex"/>
   <affected-histogram name="SimpleCache.CreationToIndexFail"/>
+  <affected-histogram name="SimpleCache.DiskCreateLatency"/>
   <affected-histogram name="SimpleCache.EntryCreatedAndStream2Omitted"/>
   <affected-histogram name="SimpleCache.EntryCreationResult"/>
   <affected-histogram name="SimpleCache.EntryCreationTime"/>
@@ -119849,6 +119874,8 @@ from previous Chrome versions.
   <affected-histogram name="SimpleCache.MaxCacheSizeOnInit"/>
   <affected-histogram name="SimpleCache.OpenEntryIndexState"/>
   <affected-histogram name="SimpleCache.PercentFullOnInit"/>
+  <affected-histogram name="SimpleCache.QueueLatency.CreateEntry"/>
+  <affected-histogram name="SimpleCache.QueueLatency.OpenEntry"/>
   <affected-histogram name="SimpleCache.ReadIsParallelizable"/>
   <affected-histogram name="SimpleCache.ReadResult"/>
   <affected-histogram name="SimpleCache.StaleIndexExtraEntryCount"/>