Add chrome://tcmalloc/ to list of WebUI URLs

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 cc85b8f69fbd1a90f7a2f3fd75625340437e1f5d..babd9e565d2f3d1dd2327cb20045d08991150ed1 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -76304,6 +76304,7 @@ To add a new entry, add it with any value and run test to compute valid value.
   <int value="325375649" label="chrome://settings-frame/"/>
   <int value="361621847" label="chrome://make-metro/"/>
   <int value="554090510" label="chrome://first-run/"/>
+  <int value="581234974" label="chrome://tcmalloc/"/>

[Dan Beam, 2015/11/18 18:30:54]

this number brought to you by:

LOG(ERROR) << static_cast<base::HistogramBase::Sample>(
    base::Hash(GURL("chrome://tcmalloc/").GetOrigin().spec()));

   <int value="646837226" label="chrome://crashes/"/>
   <int value="659389881" label="chrome://gpu/"/>
   <int value="689991895" label="chrome://supervised-user-internals/"/>