Add metric for deleting omnibox text on Android.

Adds the MobileOmniboxDeleteUrl metric and records it whenever the user
clears the contents of the omnibox with the delete button.

Change-Id: Idddeccb89999ceeea45873a05ba2b052f0e7d2d2
Reviewed-on: https://chromium-review.googlesource.com/892140Reviewed-by: Maria Khomenko <mariakhomenko@chromium.org>
Reviewed-by: Mark Pearson <mpearson@chromium.org>
Commit-Queue: Troy Hildebrandt <thildebr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533033}

chrome/android/java/src/org/chromium/chrome/browser/omnibox/LocationBarLayout.java

@@ -1942,6 +1942,7 @@ public class LocationBarLayout extends FrameLayout
             }
 
             startZeroSuggest();
+            RecordUserAction.record("MobileOmniboxDeleteUrl");
             return;
         } else if (!mUrlHasFocus && shouldShowPageInfoForView(v)) {
             if (mToolbarDataProvider.hasTab() && getCurrentTab().getWebContents() != null

tools/metrics/actions/actions.xml

@@ -12032,6 +12032,13 @@ should be able to be added at any place in this file.
   <description>Please enter the description of the metric.</description>
 </action>
 
+<action name="MobileOmniboxDeleteUrl">
+  <owner>thildebr@chromium.org</owner>
+  <description>
+    The user cleared the contents of the omnibox via the delete button.
+  </description>
+</action>
+
 <action name="MobileOmniboxRefineSuggestion">
   <obsolete>
     Deprecated 07/2017. Replaced by MobileOmniboxRefineSuggestion.Query and