Adding UMA to track previews opt outs and blacklist eligibility

components/previews/core/previews_io_data.cc

Index: components/previews/core/previews_io_data.cc
diff --git a/components/previews/core/previews_io_data.cc b/components/previews/core/previews_io_data.cc
index 496ef6dd69141a7c0af73634837ad38984b1c451..71ead03890e675e05a53966347bd145e84965021 100644
--- a/components/previews/core/previews_io_data.cc
+++ b/components/previews/core/previews_io_data.cc
@@ -2,32 +2,50 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/previews/core/previews_io_data.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/files/file_path.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram.h"
 #include "base/sequenced_task_runner.h"
 #include "base/time/default_clock.h"
 #include "components/previews/core/previews_black_list.h"
 #include "components/previews/core/previews_opt_out_store.h"
 #include "components/previews/core/previews_ui_service.h"
 #include "net/nqe/network_quality_estimator.h"
 #include "net/url_request/url_request.h"
 #include "net/url_request/url_request_context.h"
 #include "url/gurl.h"
 
 namespace previews {
 
+namespace {
+
+void LogPreviewsEligibilityReason(PreviewsEligibilityReason status,
+                                  PreviewsType type) {
+  switch (type) {
+    case PreviewsType::OFFLINE:
+      UMA_HISTOGRAM_ENUMERATION(
+          "Previews.EligibilityReason.Offline", static_cast<int>(status),

[tbansal1, 2016/11/08 00:30:52]

I would use Previews.Offline.EligibilityReason to ensure that all Offline
histograms have same prefix (similar to PageLoad.Clients.DataReductionProxy.*).

[RyanSturm, 2016/11/08 22:22:29]

Like above, I was just going to suffix with the type (this doesn't make anything
harder in a workflow AFAIK).

+          static_cast<int>(PreviewsEligibilityReason::LAST));
+      break;
+    default:
+      NOTREACHED();
+  }
+}
+
+}  // namespace
+
 PreviewsIOData::PreviewsIOData(
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
     const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner)
     : ui_task_runner_(ui_task_runner),
       io_task_runner_(io_task_runner),
       weak_factory_(this) {}
 
 PreviewsIOData::~PreviewsIOData() {}
 
 void PreviewsIOData::Initialize(
@@ -66,26 +84,40 @@ void PreviewsIOData::ClearBlackList(base::Time begin_time,
   DCHECK(io_task_runner_->BelongsToCurrentThread());
   previews_black_list_->ClearBlackList(begin_time, end_time);
 }
 
 bool PreviewsIOData::ShouldAllowPreview(const net::URLRequest& request,
                                         PreviewsType type) const {
   if (!IsPreviewsTypeEnabled(type))
     return false;
   // The blacklist will disallow certain hosts for periods of time based on
   // user's opting out of the preview
-  if (!previews_black_list_ ||
-      !previews_black_list_->IsLoadedAndAllowed(request.url(), type)) {
+  if (!previews_black_list_) {
+    LogPreviewsEligibilityReason(
+        PreviewsEligibilityReason::BLACKLIST_UNAVAILABLE, type);
+    return false;
+  }
+  PreviewsEligibilityReason status =
+      previews_black_list_->IsLoadedAndAllowed(request.url(), type);
+  if (status != PreviewsEligibilityReason::ALLOWED) {
+    LogPreviewsEligibilityReason(status, type);
     return false;
   }
   net::NetworkQualityEstimator* network_quality_estimator =
       request.context()->network_quality_estimator();
-  if (!network_quality_estimator)
+  if (!network_quality_estimator ||
+      network_quality_estimator->GetEffectiveConnectionType() <
+          net::EFFECTIVE_CONNECTION_TYPE_OFFLINE) {
+    LogPreviewsEligibilityReason(
+        PreviewsEligibilityReason::NETWORK_QUALITY_UNAVAILABLE, type);
     return false;
-
-  net::EffectiveConnectionType effective_connection_type =
-      network_quality_estimator->GetEffectiveConnectionType();
-  return effective_connection_type >= net::EFFECTIVE_CONNECTION_TYPE_OFFLINE &&
-         effective_connection_type <= net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G;
+  }
+  if (network_quality_estimator->GetEffectiveConnectionType() >
+      net::EFFECTIVE_CONNECTION_TYPE_SLOW_2G) {
+    LogPreviewsEligibilityReason(PreviewsEligibilityReason::NETWORK_NOT_SLOW,
+                                 type);
+    return false;
+  }
+  return true;

[tbansal1, 2016/11/08 00:30:52]

Add:
LogPreviewsEligibilityReason(PreviewsEligibilityReason::ALLOWED, type);
before returning true?

[tbansal1, 2016/11/08 00:30:52]

Also, add a test to components/previews/core/previews_io_data_unittest.cc that
checks for histogram correctness?

[RyanSturm, 2016/11/08 22:22:29]

Done.

[RyanSturm, 2016/11/08 22:22:29]

Done.

 }
 
 }  // namespace previews