Add support to previews/ for Server LoFi and LitePages

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 9645fa249513ccc186559024eee32088444a2ec5..b80752848f424621cebe2bb9e67dde2e4ef712a9 100644
--- a/components/previews/core/previews_io_data.cc
+++ b/components/previews/core/previews_io_data.cc
@@ -28,16 +28,61 @@ namespace {
 void LogPreviewsEligibilityReason(PreviewsEligibilityReason status,
                                   PreviewsType type) {
   switch (type) {
+    case PreviewsType::LITE_PAGE:
+      UMA_HISTOGRAM_ENUMERATION(
+          "Previews.EligibilityReason.LitePage", static_cast<int>(status),

[tbansal1, 2017/03/20 22:55:13]

Maybe use histogram factory here to avoid code duplication?

[RyanSturm, 2017/05/02 20:08:12]

Done.

+          static_cast<int>(PreviewsEligibilityReason::LAST));
+      break;
+    case PreviewsType::SERVER_LOFI:
+      UMA_HISTOGRAM_ENUMERATION(
+          "Previews.EligibilityReason.ServerLoFi", static_cast<int>(status),
+          static_cast<int>(PreviewsEligibilityReason::LAST));
+      break;
     case PreviewsType::OFFLINE:
       UMA_HISTOGRAM_ENUMERATION(
           "Previews.EligibilityReason.Offline", static_cast<int>(status),
           static_cast<int>(PreviewsEligibilityReason::LAST));
       break;
-    default:
+    case PreviewsType::NONE:
+    case PreviewsType::LAST:
       NOTREACHED();
   }
 }
 
+bool ShouldCheckNetworkQuality(PreviewsType type) {

[tbansal1, 2017/03/20 22:55:13]

May be change it to return the ECT  threshold?
and if ECT_LAST is returned, then do not check the network conditions?

[RyanSturm, 2017/05/02 20:08:12]

Acknowledged.

+  switch (type) {
+    // These types check network qualtiy on their own.
+    case PreviewsType::LITE_PAGE:
+    case PreviewsType::SERVER_LOFI:
+      return false;
+    // These types use the default previews network quality behavior.
+    case PreviewsType::OFFLINE:
+      return true;
+    case PreviewsType::NONE:
+    case PreviewsType::LAST:
+      break;
+  }
+  NOTREACHED();
+  return false;
+}
+
+bool AllowedOnReload(PreviewsType type) {
+  switch (type) {
+    // These types return new content on refresh.
+    case PreviewsType::LITE_PAGE:
+    case PreviewsType::SERVER_LOFI:
+      return true;
+    // Loading these types will always be stale when refreshed.
+    case PreviewsType::OFFLINE:
+      return false;
+    case PreviewsType::NONE:
+    case PreviewsType::LAST:
+      break;
+  }
+  NOTREACHED();
+  return false;
+}
+
 }  // namespace
 
 PreviewsIOData::PreviewsIOData(
@@ -106,29 +151,31 @@ bool PreviewsIOData::ShouldAllowPreview(const net::URLRequest& request,
     LogPreviewsEligibilityReason(status, type);
     return false;
   }
-  net::NetworkQualityEstimator* network_quality_estimator =
-      request.context()->network_quality_estimator();
-  if (!network_quality_estimator ||
-      network_quality_estimator->GetEffectiveConnectionType() <
-          net::EFFECTIVE_CONNECTION_TYPE_OFFLINE) {
-    LogPreviewsEligibilityReason(
-        PreviewsEligibilityReason::NETWORK_QUALITY_UNAVAILABLE, type);
-    return false;
-  }
-  if (network_quality_estimator->GetEffectiveConnectionType() >
-      params::EffectiveConnectionTypeThreshold()) {
-    LogPreviewsEligibilityReason(PreviewsEligibilityReason::NETWORK_NOT_SLOW,
-                                 type);
-    return false;
-  }
-  // LOAD_VALIDATE_CACHE or LOAD_BYPASS_CACHE mean the user reloaded the page.
-  // If this is a query for offline previews, reloads should be disallowed.
-  if (type == PreviewsType::OFFLINE &&
-      request.load_flags() &
-          (net::LOAD_VALIDATE_CACHE | net::LOAD_BYPASS_CACHE)) {
-    LogPreviewsEligibilityReason(
-        PreviewsEligibilityReason::RELOAD_DISALLOWED_FOR_OFFLINE, type);
-    return false;
+  if (ShouldCheckNetworkQuality(type)) {

[tbansal1, 2017/03/20 22:55:13]

nit: it might be more readable to move this (including all the ECT related
stuff) to a separate method.

[RyanSturm, 2017/05/02 20:08:12]

Done.

+    net::NetworkQualityEstimator* network_quality_estimator =
+        request.context()->network_quality_estimator();
+    if (!network_quality_estimator ||
+        network_quality_estimator->GetEffectiveConnectionType() <
+            net::EFFECTIVE_CONNECTION_TYPE_OFFLINE) {
+      LogPreviewsEligibilityReason(
+          PreviewsEligibilityReason::NETWORK_QUALITY_UNAVAILABLE, type);
+      return false;
+    }
+    if (network_quality_estimator->GetEffectiveConnectionType() >
+        params::EffectiveConnectionTypeThreshold()) {
+      LogPreviewsEligibilityReason(PreviewsEligibilityReason::NETWORK_NOT_SLOW,
+                                   type);
+      return false;
+    }
+    // LOAD_VALIDATE_CACHE or LOAD_BYPASS_CACHE mean the user reloaded the page.
+    // If this is a query for offline previews, reloads should be disallowed.
+    if (!AllowedOnReload(type) &&
+        request.load_flags() &
+            (net::LOAD_VALIDATE_CACHE | net::LOAD_BYPASS_CACHE)) {
+      LogPreviewsEligibilityReason(PreviewsEligibilityReason::RELOAD_DISALLOWED,
+                                   type);
+      return false;
+    }
   }
   LogPreviewsEligibilityReason(PreviewsEligibilityReason::ALLOWED, type);
   return true;