Validate that zip entry filenames are UTF8.

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 bc7a43e7e94c75b84eaca3097f58a92f08b2a715..31e94ff2de596804004fdae6444ac2637223ce91 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -32659,6 +32659,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="SBClientDownload.ZipFileHasUnsafeFile" enum="BooleanHit">

[Mark P, 2015/03/24 18:13:34]

Do you feel that BooleanHit is somehow more appropriate than Boolean here?

+  <owner>grt@chromium.org</owner>
+  <summary>
+    Hit if a zip file analyzed by the SafeBrowsing download service contains a
+    file with an unsafe name.

[Mark P, 2015/03/24 18:13:34]

For clarity, perhaps add something like (if true):
Emitted each time a zip file is successfully downloaded and analyzed.

+  </summary>
+</histogram>
+
 <histogram name="SBClientMalware.ClassificationStart" enum="BooleanHit">
   <owner>noelutz@chromium.org</owner>
   <summary>