ash:Shelf - Added UMA stats for ShelfAlignment

ash/shelf/shelf_view.cc

Index: ash/shelf/shelf_view.cc
diff --git a/ash/shelf/shelf_view.cc b/ash/shelf/shelf_view.cc
index 1257032b2101fafc5640d5d7d2199ca44a153ba9..173f6a3ca037a5dd382fbedd90350d305f5b8d29 100644
--- a/ash/shelf/shelf_view.cc
+++ b/ash/shelf/shelf_view.cc
@@ -27,6 +27,7 @@
 #include "ash/shell_delegate.h"
 #include "base/auto_reset.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/histogram.h"
 #include "grit/ash_resources.h"
 #include "grit/ash_strings.h"
 #include "ui/aura/client/screen_position_client.h"
@@ -58,6 +59,11 @@ using views::View;
 namespace ash {
 namespace internal {
 
+const int SHELF_ALIGNMENT_UMA_ENUM_VALUE_BOTTOM = 0;
+const int SHELF_ALIGNMENT_UMA_ENUM_VALUE_LEFT = 1;
+const int SHELF_ALIGNMENT_UMA_ENUM_VALUE_RIGHT = 2;
+const int SHELF_ALIGNMENT_UMA_ENUM_VALUE_COUNT = 3;
+
 // Default amount content is inset on the left edge.
 const int kDefaultLeadingInset = 8;
 
@@ -1526,9 +1532,9 @@ void ShelfView::PointerPressedOnButton(views::View* view,
       model_->items()[index].id);
   if (view_model_->view_size() <= 1 || !item_delegate->IsDraggable())
     return;  // View is being deleted or not draggable, ignore request.
-
   drag_view_ = view;
   drag_offset_ = layout_manager_->PrimaryAxisValue(event.x(), event.y());
+  RecordCurrentAlignmentForUMAHistogram("Ash.ShelfAlignmentUsage");
 }
 
 void ShelfView::PointerDraggedOnButton(views::View* view,
@@ -1884,5 +1890,16 @@ int ShelfView::CalculateShelfDistance(const gfx::Point& coordinate) const {
   return distance > 0 ? distance : 0;
 }
 
+void ShelfView::RecordCurrentAlignmentForUMAHistogram(
+    const char* histogram_name) {
+  UMA_HISTOGRAM_ENUMERATION(histogram_name,

[James Cook, 2013/10/30 16:49:12]

This won't work. UMA_HISTOGRAM_ENUMERATION does some magic with the current
file/line name to create a cached value - it needs a literal string at the call
site.  This is why ChromeShellDelegate::RecordUserMetricsAction() has a huge
switch.  It might be better to pull out the shelf alignment into the sites that
are recording it and put the strings there.

If you really need to build histograms out of a string see
RecordLinearHistogram() in oom_priority_manager.cc for an example.

+      layout_manager_->SelectValueForShelfAlignment(
+          SHELF_ALIGNMENT_UMA_ENUM_VALUE_BOTTOM,
+          SHELF_ALIGNMENT_UMA_ENUM_VALUE_LEFT,
+          SHELF_ALIGNMENT_UMA_ENUM_VALUE_RIGHT,
+          -1),
+      SHELF_ALIGNMENT_UMA_ENUM_VALUE_COUNT);
+}
+
 }  // namespace internal
 }  // namespace ash