[ash-md] Added Ash.Wallpaper.TimeSpentResizing histogram.

This will track the amount of time spent resizing wallpapers.

BUG=710493

Review-Url: https://codereview.chromium.org/2808353003
Cr-Commit-Position: refs/heads/master@{#464521}

components/wallpaper/wallpaper_resizer.cc

@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/task_runner.h"
 #include "components/wallpaper/wallpaper_resizer_observer.h"
 #include "third_party/skia/include/core/SkImage.h"
@@ -121,6 +122,8 @@ WallpaperResizer::~WallpaperResizer() {
 }
 
 void WallpaperResizer::StartResize() {
+  start_calculation_time_ = base::TimeTicks::Now();
+
   SkBitmap* resized_bitmap = new SkBitmap;
   if (!task_runner_->PostTaskAndReply(
           FROM_HERE,
@@ -144,6 +147,9 @@ void WallpaperResizer::RemoveObserver(WallpaperResizerObserver* observer) {
 
 void WallpaperResizer::OnResizeFinished(SkBitmap* resized_bitmap) {
   image_ = gfx::ImageSkia::CreateFrom1xBitmap(*resized_bitmap);
+  UMA_HISTOGRAM_TIMES("Ash.Wallpaper.TimeSpentResizing",
+                      base::TimeTicks::Now() - start_calculation_time_);
+
   for (auto& observer : observers_)
     observer.OnWallpaperResized();
 }

components/wallpaper/wallpaper_resizer.h

@@ -11,6 +11,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
+#include "base/time/time.h"
 #include "components/wallpaper/wallpaper_layout.h"
 #include "components/wallpaper/wallpaper_resizer_observer.h"
 #include "skia/ext/image_operations.h"
@@ -73,6 +74,10 @@ class WALLPAPER_EXPORT WallpaperResizer {
 
   WallpaperLayout layout_;
 
+  // The time that StartResize() was last called. Used for recording timing
+  // metrics.
+  base::TimeTicks start_calculation_time_;
+
   scoped_refptr<base::TaskRunner> task_runner_;
 
   base::WeakPtrFactory<WallpaperResizer> weak_ptr_factory_;

tools/metrics/histograms/histograms.xml

@@ -2320,6 +2320,17 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Ash.Wallpaper.TimeSpentResizing" units="ms">
+  <owner>bruthig@chromium.org</owner>
+  <owner>tbuckley@chromium.org</owner>
+  <summary>
+    The time taken to resize wallpapers. Recorded once each time the wallpaper
+    changes (e.g. initial wallpaper loading at boot, switching user avatar at
+    login screen, switching between logged in users, user selects new wallpaper,
+    etc).
+  </summary>
+</histogram>
+
 <histogram name="Ash.Wallpaper.Type" enum="WallpaperType">
   <owner>kuscher@google.com</owner>
   <summary>The wallpaper type. Recorded at user login.</summary>