Added UMA statistics for changing the active window via click or touch events.

ui/wm/core/default_activation_client.cc

Index: ui/wm/core/default_activation_client.cc
diff --git a/ui/wm/core/default_activation_client.cc b/ui/wm/core/default_activation_client.cc
index 20c0d79b7dc7fd121c7d21c236ce38e34581bc1b..e48418450652e5563c460ac1654d94c3466e410c 100644
--- a/ui/wm/core/default_activation_client.cc
+++ b/ui/wm/core/default_activation_client.cc
@@ -59,6 +59,14 @@ void DefaultActivationClient::RemoveObserver(
 }
 
 void DefaultActivationClient::ActivateWindow(aura::Window* window) {
+  ActivateWindowImpl(aura::client::ActivationChangeObserver::ActivationReason::
+                         ACTIVATION_CLIENT,
+                     window);
+}
+
+void DefaultActivationClient::ActivateWindowImpl(
+    aura::client::ActivationChangeObserver::ActivationReason reason,
+    aura::Window* window) {
   aura::Window* last_active = GetActiveWindow();
   if (last_active == window)
     return;
@@ -69,24 +77,28 @@ void DefaultActivationClient::ActivateWindow(aura::Window* window) {
   window->parent()->StackChildAtTop(window);
   window->AddObserver(this);
 
-  FOR_EACH_OBSERVER(aura::client::ActivationChangeObserver,
-                    observers_,
-                    OnWindowActivated(window, last_active));
+  FOR_EACH_OBSERVER(aura::client::ActivationChangeObserver, observers_,
+                    OnWindowActivated(reason, window, last_active));
 
   aura::client::ActivationChangeObserver* observer =
       aura::client::GetActivationChangeObserver(last_active);
-  if (observer)
-    observer->OnWindowActivated(window, last_active);
+  if (observer) {
+    observer->OnWindowActivated(reason, window, last_active);
+  }
   observer = aura::client::GetActivationChangeObserver(window);
-  if (observer)
-    observer->OnWindowActivated(window, last_active);
+  if (observer) {
+    observer->OnWindowActivated(reason, window, last_active);
+  }
 }
 
 void DefaultActivationClient::DeactivateWindow(aura::Window* window) {
   aura::client::ActivationChangeObserver* observer =
       aura::client::GetActivationChangeObserver(window);
-  if (observer)
-    observer->OnWindowActivated(NULL, window);
+  if (observer) {
+    observer->OnWindowActivated(aura::client::ActivationChangeObserver::
+                                    ActivationReason::ACTIVATION_CLIENT,
+                                NULL, window);
+  }
   if (last_active_)
     ActivateWindow(last_active_);
 }
@@ -121,8 +133,10 @@ void DefaultActivationClient::OnWindowDestroyed(aura::Window* window) {
     active_windows_.pop_back();
     aura::Window* next_active = GetActiveWindow();
     if (next_active && aura::client::GetActivationChangeObserver(next_active)) {
-      aura::client::GetActivationChangeObserver(next_active)->OnWindowActivated(
-          next_active, NULL);
+      aura::client::GetActivationChangeObserver(next_active)
+          ->OnWindowActivated(aura::client::ActivationChangeObserver::
+                                  ActivationReason::WINDOW_DISPOSITION_CHANGED,
+                              next_active, NULL);
     }
     return;
   }