Add UMA metrics for the time it takes to read store from disk and apply update

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 e4e29aeeb7dda960671391a639ab42e29e5de9e1..d4f2563cddc46dab5c85c52d83dd9ee6b8658bd3 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -50717,6 +50717,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SafeBrowsing.V4AddUnlumpedHashesTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to copy the SafeBrowsing list update as a string,
+    into a map which contains the hash prefixes that are looked up when a client
+    queries for the reputation of a resource (URL, full hash, etc.).
+  </summary>
+</histogram>
+
 <histogram name="SafeBrowsing.V4ApplyUpdateResult"
     enum="SafeBrowsingV4ApplyUpdateResult">
   <owner>vakh@chromium.org</owner>
@@ -50745,6 +50754,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SafeBrowsing.V4DecodeAdditionsTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to decode the Rice-encoded additions to the
+    blacklist into raw format.
+  </summary>
+</histogram>
+
 <histogram name="SafeBrowsing.V4DecodeRemovalsResult"
     enum="SafeBrowsingV4DecodeResult">
   <owner>vakh@chromium.org</owner>
@@ -50755,6 +50772,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="SafeBrowsing.V4DecodeRemovalsTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to decode the Rice-encoded removals from the
+    blacklist into raw format.
+  </summary>
+</histogram>
+
 <histogram name="SafeBrowsing.V4FullHashCacheResult"
     enum="SafeBrowsingV4FullHashCacheResult">
   <owner>kcarattini@chromium.org</owner>
@@ -50769,6 +50794,47 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Track get hash response hits for V4 full hash requests.</summary>
 </histogram>
 
+<histogram name="SafeBrowsing.V4MergeUpdateTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to merge the existing state of the list with the
+    update. The update may have been received from the server, or it may have
+    just been read from disk.
+  </summary>
+</histogram>
+
+<histogram name="SafeBrowsing.V4ProcessFullUpdateTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to process a SafeBrowsing list full update. It
+    includes V4AddUnlumpedHashesTime for each prefix-sized list, and
+    V4MergeUpdateTime. Additionally, if the update is Rice-encoded, it includes
+    V4DecodeAdditionsTime for each prefix-sized list that's Rice-encoded.
+  </summary>
+</histogram>
+
+<histogram name="SafeBrowsing.V4ProcessPartialUpdateTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to process a SafeBrowsing list partial update. It
+    includes V4AddUnlumpedHashesTime for each prefix-sized list, and
+    V4MergeUpdateTime. Additionally, if the update is Rice-encoded, it includes
+    V4DecodeRemovalsTime, and V4DecodeAdditionsTime for each prefix-sized list
+    that's Rice-encoded.
+  </summary>
+</histogram>
+
+<histogram name="SafeBrowsing.V4ReadFromDiskTime" units="ms">
+  <owner>vakh@chromium.org</owner>
+  <summary>
+    Records the time it takes to read, parse, and process a SafeBrowsing list
+    stored on disk. This happens at Chromium start-up. It includes
+    V4AddUnlumpedHashesTime for each prefix-sized list, and V4MergeUpdateTime.
+    Additionally, if the file is Rice-encoded, it includes V4DecodeAdditionsTime
+    for each prefix-sized list that's Rice-encoded.
+  </summary>
+</histogram>
+
 <histogram name="SafeBrowsing.V4StoreReadResult"
     enum="SafeBrowsingV4StoreReadResult">
   <owner>vakh@chromium.org</owner>