Add histograms for notification icons.

content/child/notifications/notification_image_loader.cc

Index: content/child/notifications/notification_image_loader.cc
diff --git a/content/child/notifications/notification_image_loader.cc b/content/child/notifications/notification_image_loader.cc
index 08a108a33b30e207c29f5fad895a77f53791bd88..0cdd71606ab59847d789ae7f1e84642b48a2921a 100644
--- a/content/child/notifications/notification_image_loader.cc
+++ b/content/child/notifications/notification_image_loader.cc
@@ -7,6 +7,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "content/child/image_decoder.h"
 #include "third_party/WebKit/public/platform/Platform.h"
@@ -39,6 +40,8 @@ void NotificationImageLoader::StartOnMainThread(const GURL& image_url) {
   DCHECK(main_task_runner_->BelongsToCurrentThread());
   DCHECK(!url_loader_);
 
+  start_time_ = base::TimeTicks::Now();
+
   WebURL image_web_url(image_url);
   WebURLRequest request(image_web_url);
   request.setRequestContext(WebURLRequest::RequestContextImage);
@@ -63,6 +66,9 @@ void NotificationImageLoader::didFinishLoading(
     int64_t total_encoded_data_length) {
   DCHECK(!completed_);
 
+  UMA_HISTOGRAM_LONG_TIMES("Notifications.Icon.LoadFinishTime",
+                           base::TimeTicks::Now() - start_time_);
+
   RunCallbackOnWorkerThread();
 }
 
@@ -71,6 +77,9 @@ void NotificationImageLoader::didFail(WebURLLoader* loader,
   if (completed_)
     return;
 
+  UMA_HISTOGRAM_LONG_TIMES("Notifications.Icon.LoadFailTime",
+                           base::TimeTicks::Now() - start_time_);
+
   RunCallbackOnWorkerThread();
 }
 
@@ -89,6 +98,10 @@ void NotificationImageLoader::RunCallbackOnWorkerThread() {
 
 SkBitmap NotificationImageLoader::GetDecodedImage() const {
   DCHECK(completed_);
+
+  UMA_HISTOGRAM_CUSTOM_COUNTS("Notifications.Icon.Size", buffer_.size(), 1,
+                              10000000 /* ~10mb */, 50);

[Peter Beverloo, 2016/02/19 17:13:44]

Perhaps this would be better named "FileSize" to distinguish from "ImageSize"?

We have 50 buckets from 0 to 10000000 bytes, which means that buckets increment
in steps of 200KB. It seems to me that most images, especially icons, will be
stuck in the first few buckets?

I think a more reasonable range would be from 0 to 1000000 bytes (1MB), which
happens to be provided by the UMA_HISTOGRAM_COUNTS macro. This gives us 20KB
increments.

(If the overflow bucket is large the next steps will most likely be in the
realms of dev advocacy :-).)

[Ilya Sherman, 2016/02/19 17:16:58]

Note that histogram buckets are exponentially sized, rather than linearly sized.
 So, you should still have relatively fine resolution at the low end, even with
a 10MB upper bound.

+1 to the "FileSize" suggestion.

[Michael van Ouwerkerk, 2016/02/22 17:24:32]

Done.

[Michael van Ouwerkerk, 2016/02/22 17:24:32]

Renamed to "FileSize".

+
   if (buffer_.empty())
     return SkBitmap();