Add UMA stats to record when DLLs are successfully blocked in the Browser.

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 2060650ef36443c9e690a9b15ec3bffbe863e66d..f69beeb07be5617e8b2931abdffcfb9dc315433e 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1376,6 +1376,13 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Blacklist.Blocked" units="DllHash">
+  <summary>
+    Records the name hashes of all the dlls that are blocked from the browser
+    process.
+  </summary>
+</histogram>
+
 <histogram name="Blacklist.PatchedInRenderer" enum="BooleanHit">
   <summary>
     Counts the number of times a renderer process is started with the browser
@@ -25468,6 +25475,15 @@ other types of suffix sets.
   <int value="20" label="SQLite Integrity Web Data Test"/>
 </enum>
 
+<enum name="DllHash" type="int">
+<!-- Generated by chrome_elf/dll_hash_for_uma/dll_hash_for_uma_main.cc -->
+
+  <int value="803283353" label="lmrn.dll"/>
+  <int value="989714890" label="datamngr.dll"/>
+  <int value="1270622879" label="hk.dll"/>
+  <int value="2132270559" label="libsvn_tsvn32.dll"/>
+</enum>
+
 <enum name="DNSEmptyAddressListAndNoError" type="int">
   <int value="0" label="Error reported or Address List is not empty"/>
   <int value="1" label="Success reported but Address List is empty"/>