Finch experiment: auto-detect text encoding

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 e935388f8e17010c14afcea042543e834b592d4b..62d43e268da4ca2e82bfc3335037dedf1ffd2ad0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -2044,6 +2044,30 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="AutodetectEncoding.Attempted" enum="BooleanAttempted">
+  <owner>jinsukkim@chromium.org</owner>
+  <summary>
+    Whether the text encoding auto detection logic was attempted for a web page.
+    The logic is triggered when the parser fails to find the encoding method
+    from other signals such as http header, meta tag, BOM, etc.
+
+    If the logic successfully detects a new encoding method which is different
+    from the default one, the result is reported through
+    AutodetectEncoding.Detected with the encoding method (see below). Otherwise
+    - i.e. detection logic somehow fails to work for the page or the detected
+    one is same as the default - no result is reported.
+  </summary>
+</histogram>
+
+<histogram name="AutodetectEncoding.Detected" enum="EncodingMethod"
+    units="pages">
+  <owner>jinsukkim@chromium.org</owner>
+  <summary>
+    The number of web pages whose encoding method is found by the auto detection
+    logic. Grouped by the encoding methods defined in EncodingMethod.
+  </summary>
+</histogram>
+
 <histogram name="Autofill.AddressBook.AccessSkipped" enum="BooleanSkipped">
   <obsolete>
     Deprecated as of 8/2015.
@@ -58017,6 +58041,46 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="9" label="SCRIPT_READ_FINISHED"/>
 </enum>
 
+<enum name="EncodingMethod" type="int">

[jwd, 2015/12/07 23:43:07]

Alternatively, you could hash the encoding name, and log it to a sparse
histogram. You'd still populate this enum, with the hash to label mapping. Any
encoding methods you missed would show up as unlabeled buckets, and you could
update histogram.xml when you figure out what they are. The added cost is that
writing to a sparse histogram is more expensive (requires a lock), and all the
unknowns won't be counted in one place.

Up to you. I'm fine with how it is.

[Jinsuk Kim, 2015/12/08 00:09:42]

Thanks for letting me know about sparse histogram which I was not aware of. I
think enum only is simple and enough for the experiment. Let me keep what's been
done here.

+  <int value="0" label="UNKNOWN"/>
+  <int value="1" label="Big5"/>
+  <int value="2" label="EUC-JP"/>
+  <int value="3" label="EUC-KR"/>
+  <int value="4" label="GBK"/>
+  <int value="5" label="IBM866"/>
+  <int value="6" label="ISO-2022-JP"/>
+  <int value="7" label="ISO-8859-10"/>
+  <int value="8" label="ISO-8859-13"/>
+  <int value="9" label="ISO-8859-14"/>
+  <int value="10" label="ISO-8859-15"/>
+  <int value="11" label="ISO-8859-16"/>
+  <int value="12" label="ISO-8859-2"/>
+  <int value="13" label="ISO-8859-3"/>
+  <int value="14" label="ISO-8859-4"/>
+  <int value="15" label="ISO-8859-5"/>
+  <int value="16" label="ISO-8859-6"/>
+  <int value="17" label="ISO-8859-7"/>
+  <int value="18" label="ISO-8859-8"/>
+  <int value="19" label="ISO-8859-8-I"/>
+  <int value="20" label="KOI8-R"/>
+  <int value="21" label="KOI8-U"/>
+  <int value="22" label="Shift_JIS"/>
+  <int value="23" label="UTF-16LE"/>
+  <int value="24" label="UTF-8"/>
+  <int value="25" label="gb18030"/>
+  <int value="26" label="macintosh"/>
+  <int value="27" label="windows-1250"/>
+  <int value="28" label="windows-1251"/>
+  <int value="29" label="windows-1252"/>
+  <int value="30" label="windows-1253"/>
+  <int value="31" label="windows-1254"/>
+  <int value="32" label="windows-1255"/>
+  <int value="33" label="windows-1256"/>
+  <int value="34" label="windows-1257"/>
+  <int value="35" label="windows-1258"/>
+  <int value="36" label="windows-874"/>
+</enum>
+
 <enum name="EnhancedBookmarkViewMode" type="int">
   <obsolete>
     Deprecated 9/2015.