Compile-time and run-time flags for top chrome material design.

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 2143fbfa0ae2a0aad93bd63d77c8797cb9e0e766..27d9259561b60334b5b2d46576194cce8fe3cd3b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -41747,6 +41747,13 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Number of retries until the final response was recorded.</summary>
 </histogram>
 
+<histogram name="TopChromeMD">

[Alexei Svitkine (slow), 2015/05/22 16:56:43]

I don't see where you're logging this histogram. Could you clarify?

Also, it would be better not to introduce a new top-level prefix for just one
histogram - better to find an existing place where you can nest it under.

Finally, it looks like this is a histogram with two possible values, so instead
of having two separate histograms (as you've defined via histogram_suffixes),
it's better to use an enumerated histogram.

+  <owner>girard@google.com</owner>
+  <summary>
+    Enables or disables the material design style in the Chrome Browser.
+  </summary>
+</histogram>
+
 <histogram name="TopSites.NumberOfApplyBlacklist">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>The number of times TopSitesImpl::ApplyBlacklist is called.</summary>
@@ -68585,6 +68592,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="ThreadWatcher.UnresponsiveThreads"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="TopChromeMDFlags">
+  <suffix name="TopChromeMDEnabled"/>
+  <suffix name="TopChromeMDDisabled"/>
+  <affected-histogram name="TopChromeMD"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="Tps65090Fets" separator=".">
   <suffix name="Fet1" label="FET1 on tps65090 (register 0xf)"/>
   <suffix name="Fet2" label="FET2 on tps65090 (register 0x10)"/>