SimpleCache: open with fewer seeks.

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 03604c2c3be284aad428fc627180c303fbec889f..0d531ac66e310655de486da3032c81d62f745044 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -50498,6 +50498,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
 </histogram>
 
 <histogram name="SimpleCache.KeyMatchedOnOpen" enum="BooleanMatched">
+  <obsolete>
+    Deprecated 2016-05 as the match checking was moved back into the entry
+    itself, so this result is now reported in the SimpleCache.x.SyncOpenResult
+    histograms.
+  </obsolete>
   <owner>gavinp@chromium.org</owner>
   <summary>
     For each call to OpenEntry, whether the key on disk matched the request key.
@@ -50578,6 +50583,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SimpleCache.SyncCheckEOFHasKeySHA256" enum="BooleanHasSHA256">
+  <owner>gavinp@chromium.org</owner>
+  <summary>
+    For each EOFRecord found with a valid magic number, indicates if the record
+    also contains a key SHA256. Only recorded for stream 0.
+  </summary>
+</histogram>
+
 <histogram name="SimpleCache.SyncCheckEOFResult"
     enum="SimpleCacheSyncCheckEOFResult">
   <owner>gavinp@chromium.org</owner>
@@ -63945,6 +63958,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Has seek penalty (e.g. spinning disk)"/>
 </enum>
 
+<enum name="BooleanHasSHA256" type="int">
+  <int value="0" label="No SHA256"/>
+  <int value="1" label="Has SHA256"/>
+</enum>
+
 <enum name="BooleanHit" type="int">
   <int value="0" label="Not_reached"/>
   <int value="1" label="Hit"/>
@@ -85856,6 +85874,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="1" label="Read Failure"/>
   <int value="2" label="Magic Number Mismatch"/>
   <int value="3" label="CRC Mismatch"/>
+  <int value="4" label="Key SHA256 Mismatch"/>
 </enum>
 
 <enum name="SimpleCacheSyncCloseResult" type="int">
@@ -85877,7 +85896,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="3" label="Bad Magic Number"/>
   <int value="4" label="Bad Version"/>
   <int value="5" label="Can't Read Key"/>
-  <int value="6" label="Key Mismatch (obsolete)"/>
+  <int value="6" label="Key Mismatch"/>
   <int value="7" label="Hash Mismatch"/>
 </enum>