Add UMA metrics for window selection and overview.

ash/wm/overview/window_selector_controller.cc

Index: ash/wm/overview/window_selector_controller.cc
diff --git a/ash/wm/overview/window_selector_controller.cc b/ash/wm/overview/window_selector_controller.cc
index f9839dcb43a7669f5ad66334d5821abc65cf33ef..c9d9e2c72f4a8ac47c0cc0c9821e8620de774dc2 100644
--- a/ash/wm/overview/window_selector_controller.cc
+++ b/ash/wm/overview/window_selector_controller.cc
@@ -6,9 +6,11 @@
 
 #include "ash/session_state_delegate.h"
 #include "ash/shell.h"
+#include "ash/shell_delegate.h"
 #include "ash/wm/mru_window_tracker.h"
 #include "ash/wm/overview/window_selector.h"
 #include "ash/wm/window_util.h"
+#include "base/metrics/histogram.h"
 
 namespace ash {
 
@@ -36,9 +38,9 @@ void WindowSelectorController::ToggleOverview() {
     if (windows.empty())
       return;
 
-    // Removing focus will hide popup windows like the omnibar or open menus.
     window_selector_.reset(
         new WindowSelector(windows, WindowSelector::OVERVIEW, this));
+    OnSelectionStarted();
   }
 }
 
@@ -54,9 +56,9 @@ void WindowSelectorController::HandleCycleWindow(
     if (windows.empty())
       return;
 
-    // Removing focus will hide popup windows like the omnibar or open menus.
     window_selector_.reset(
         new WindowSelector(windows, WindowSelector::CYCLE, this));
+    OnSelectionStarted();
     window_selector_->Step(direction);
   } else if (window_selector_->mode() == WindowSelector::CYCLE) {
     window_selector_->Step(direction);
@@ -70,10 +72,22 @@ bool WindowSelectorController::IsSelecting() {
 void WindowSelectorController::OnWindowSelected(aura::Window* window) {
   window_selector_.reset();
   wm::ActivateWindow(window);
+  last_selection_time_ = base::Time::Now();
 }
 
 void WindowSelectorController::OnSelectionCanceled() {
   window_selector_.reset();
+  last_selection_time_ = base::Time::Now();
+}
+
+void WindowSelectorController::OnSelectionStarted() {
+  if (!last_selection_time_.is_null()) {
+    Shell* shell = Shell::GetInstance();
+    shell->delegate()->RecordUserMetricsAction(UMA_WINDOW_SELECTION);

[Ilya Sherman, 2013/09/19 23:08:04]

Why is this gated on whether or not the last_selection_time_ is null?

[flackr, 2013/09/19 23:23:45]

Good catch, this should not be.

+    UMA_HISTOGRAM_LONG_TIMES(
+        "Ash.WindowSelector.TimeBetweenUse",
+        base::Time::Now() - last_selection_time_);

[Ilya Sherman, 2013/09/19 23:08:04]

Hmm, is LONG_TIMES really enough?  I'd expect it to be common to spend more than
an hour between uses of this feature.  I'd recommend using a CUSTOM_COUNTS
histogram and emitting (base::Time::Now() - last_selection_time_).InMinutes(),
covering a bigger range than just one hour.

[flackr, 2013/09/19 23:23:45]

In terms of usage, I think the exact timing beyond an hour isn't important. I'd
like to know if selection restarts very shortly after a previous selection,
indicative of choosing the wrong window and alt-tabbing again immediately, and
if power users use alt-tab / overview fairly regularly to switch windows, which
I suspect they do

+  }
 }
 
 }  // namespace ash