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 6b38741b1c42684cbc4efe6a3a8ca52982f8d5a9..08282110398d7d095b370d2434fbff45b9132988 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4820,6 +4820,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Maximal amount of memory allocated by decoder.</summary>
 </histogram>
 
+<histogram name="BrowserDialogs.ExternalProtocol.RememberCheckbox"

[Ilya Sherman, 2016/10/05 01:04:18]

Hmm, "BrowserDialogs" is more general, but I'm not quite sure that it's quite
right for the top-level name.  If you were to componentize your feature, what is
the component name that you would choose for it?  That's often a good way to
come up with a top-level UMA name as well =)

[dominickn, 2016/10/05 04:47:41]

To be honest, it would probably just be the "external protocol handler" if we
componentized it. The code is pretty small and fairly specialised. The only
thing you could really pull out is the dialog. I'm completely open to ideas
though.

[Ilya Sherman, 2016/10/05 05:57:45]

Okay.  I guess I'd be inclined to file it under "Navigation" or something like
that, but something like "BrowserDialogs" or "ExternalProtocolHandler" might be
reasonable as well.  I'll defer to your judgement as someone more familiar with
the feature than I am.  Thanks for thinking about it in some detail =)

+    enum="BooleanChecked">
+  <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.
+    Recorded each time the user interacts with the External Protocol Dialog
+    (either accepting or cancelling/dismissing).
+  </summary>
+</histogram>
+
 <histogram name="BrowserRenderProcessHost.ChildCrashes" enum="RendererType">
   <owner>wfh@chromium.org</owner>
   <summary>Count of renderer process crashes grouped by type.</summary>
@@ -72790,6 +72801,11 @@ 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"/>