Simplify the text in the external protocol confirmation dialog.

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 44130667d1c4a84e701f60e64aec9faa0c07da64..eac6ffa86e919213399a5d1ab6694f692b8c2487 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17081,6 +17081,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ExternalProtocolDialog.RememberCheckbox" enum="BooleanChecked">

[Ilya Sherman, 2016/10/04 01:34:45]

It looks like you're adding a new top-level group name,
"ExternalProtocolDialog".  Could you please check whether there is already an
existing group name that would make sense for this metric?  If not, I'd
encourage you to spend a bit of time thinking about whether this new name is
general enough.  Is there a more general, but still reasonably specific, name
that would make sense for this and related metrics?  (It might be that this is
already the best name -- I'm just generally cautious about adding new top-level
names, since they are added to what is effectively a global namespace.)

[dominickn, 2016/10/04 12:37:01]

I changed the top level name to BrowserDialogs, since ExternalProtocolDialog is
very specific. I couldn't find another top level name that seemed really
appropriate (the closest was JsDialogs, but this isn't a JsDialog).

+  <owner>dominickn@chromium.org</owner>
+  <summary>
+    Whether or not the user checked the option in the external protocol dialog
+    to remember their choice of opening or not opening the specified app.

[Ilya Sherman, 2016/10/04 01:34:45]

Please document at what point this is logged, i.e. when the dialog is closed.

[dominickn, 2016/10/04 12:37:01]

Done.

+  </summary>
+</histogram>
+
 <histogram name="FaultTolerantHeap" enum="FaultTolerantHeap">
   <owner>brucedawson@chromium.org</owner>
   <summary>
@@ -71651,6 +71659,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1" label="Changed"/>
 </enum>
 
+<enum name="BooleanChecked" type="int">
+  <int value="0" label="Not checked"/>
+  <int value="1" label="Checked"/>
+</enum>
+
 <enum name="BooleanCloseTimeout" type="int">
   <int value="0" label="Closed normally"/>
   <int value="1" label="Timed out"/>