Add UMA for app info dialog

chrome/browser/ui/app_list/app_context_menu.cc

Index: chrome/browser/ui/app_list/app_context_menu.cc
diff --git a/chrome/browser/ui/app_list/app_context_menu.cc b/chrome/browser/ui/app_list/app_context_menu.cc
index 5c454e26a82bbafe693d3979618c79298868aca8..fe95c13d09ad8c5484659867002cbda8a1ef57c5 100644
--- a/chrome/browser/ui/app_list/app_context_menu.cc
+++ b/chrome/browser/ui/app_list/app_context_menu.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/metrics/histogram.h"
 #include "chrome/app/chrome_command_ids.h"
 #include "chrome/browser/extensions/context_menu_matcher.h"
 #include "chrome/browser/extensions/menu_manager.h"
@@ -255,6 +256,7 @@ void AppContextMenu::ExecuteCommand(int command_id, int event_flags) {
   } else if (command_id == CREATE_SHORTCUTS) {
     controller_->DoCreateShortcutsFlow(profile_, app_id_);
   } else if (command_id == SHOW_APP_INFO) {
+    UMA_HISTOGRAM_ENUMERATION("Apps.AppListAppInfoDialog", 1, 2);

[benwells, 2014/07/31 06:13:18]

I think you should use UMA_HISTOGRAM_COUNTS for this, as it isn't an
enumeration.

But would it be useful to break down how often the dialog is shown for different
types of things as well as how often it is shown? Maybe we could add this as a
count, and also enumerations for the type of the app and for the location.

[sashab, 2014/08/04 00:30:45]

I was using this because it's a common pattern to measure how many users open
the dialog at least once, as opposed to how many times every user has opened the
dialog. But either way is fine.

Changed this to track:
- How many times each user has opened the the dialog
- What the location of the app is
- What the load type of the app is

     controller_->DoShowAppInfoFlow(profile_, app_id_);
   } else if (command_id >= USE_LAUNCH_TYPE_COMMAND_START &&
              command_id < USE_LAUNCH_TYPE_COMMAND_END) {