add UMA for no. of pages with no distilled data

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 4a91694e470630c5cb2b4e7392e25c3f18d8cad9..fd938d38bf164205b4901891ac45eac4bc8ea579 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -5113,6 +5113,12 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="DomDistiller.PageHasDistilledData"
+    enum="BooleanHasDistilledData">
+  <owner>kuan@chromium.org</owner>
+  <summary>Records if a page has distilled data.</summary>

[Ilya Sherman, 2014/09/27 00:30:16]

nit: "if" -> "whether"

[kuan, 2014/09/27 00:33:39]

Done.

+</histogram>
+
 <histogram name="DomDistiller.Statistics.WordCount" units="words">
   <owner>nyquist@chromium.org</owner>
   <summary>
@@ -39093,6 +39099,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="1" label="Has CRC"/>
 </enum>
 
+<enum name="BooleanHasDistilledData" type="int">
+  <int value="0" label="No distilled data"/>
+  <int value="1" label="Has distilled data"/>
+</enum>
+
 <enum name="BooleanHit" type="int">
   <int value="0" label="Not_reached"/>
   <int value="1" label="Hit"/>