[Autofill] Add FormEvent logging for "will submit form".

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 35c3c071a86a9d8d52a18c6df008a67fe2997faa..f0685134d0cd820308ebcbe5efb10f868ffd0d17 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1878,6 +1878,13 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Tracks whether Autofill is enabled when Chrome launches.</summary>
 </histogram>
 
+<histogram name="Autofill.IsFormUserSubmitted" enum="BooleanEnabled">
+  <owner>mathp@chromium.org</owner>
+  <summary>
+    Tracks whether an Autofillable form was user submitted or not.

[Evan Stade, 2015/03/18 00:45:32]

I don't think the terminology "user submitted" is very clear.

+  </summary>
+</histogram>
+
 <histogram name="Autofill.MacAddressBook" enum="AutofillMacAddressBook">
   <owner>erikchen@chromium.org</owner>
   <summary>
@@ -8895,9 +8902,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
 <histogram name="Extensions.FeatureProviderStaticInitTime" units="milliseconds">
   <owner>rkaplow@chromium.org</owner>
   <summary>
-    The amount of time that elapsed during
-    extensions::FeatureProvider::Static. Only measured while in the browser
-    process.
+    The amount of time that elapsed during extensions::FeatureProvider::Static.
+    Only measured while in the browser process.
   </summary>
 </histogram>
 
@@ -19607,8 +19613,8 @@ Therefore, the affected-histogram name has to have at least one dot in it.
     enum="QuicSessionLocations">
   <owner>rch@chromium.org</owner>
   <summary>
-    The location in quic_client_session.cc where a session is unexpectedly
-    not going away.
+    The location in quic_client_session.cc where a session is unexpectedly not
+    going away.
   </summary>
 </histogram>