Split Empty URL to a seperate Dropped Reason

Bug: 842012
Change-Id: Ifc35114d2f1a4b6045e97aa45c1c56ed96abae19
Reviewed-on: https://chromium-review.googlesource.com/1055936
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Steven Holte <holte@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559312}

components/ukm/ukm_recorder_impl.cc

@@ -97,6 +97,7 @@ enum class DroppedDataReason {
   EXTENSION_URLS_DISABLED = 6,
   EXTENSION_NOT_SYNCED = 7,
   NOT_MATCHED = 8,
+  EMPTY_URL = 9,
   NUM_DROPPED_DATA_REASONS
 };
 
@@ -342,6 +343,11 @@ void UkmRecorderImpl::UpdateSourceURL(SourceId source_id,
     return;
   }
 
+  if (unsanitized_url.is_empty()) {
+    RecordDroppedSource(DroppedDataReason::EMPTY_URL);
+    return;
+  }
+
   source_counts_.observed++;
   if (GetSourceIdType(source_id) == SourceIdType::NAVIGATION_ID)
     source_counts_.navigation_sources++;
@@ -350,6 +356,8 @@ void UkmRecorderImpl::UpdateSourceURL(SourceId source_id,
 
   if (!HasSupportedScheme(url)) {
     RecordDroppedSource(DroppedDataReason::UNSUPPORTED_URL_SCHEME);
+    DVLOG(2) << "Dropped Unsupported UKM URL:" << source_id << ":"
+             << url.spec();
     return;
   }
 

tools/metrics/histograms/enums.xml

@@ -45495,6 +45495,7 @@ Full version information for the fingerprint enum values:
   <int value="6" label="Extension URLs disabled"/>
   <int value="7" label="Extension not synced"/>
   <int value="8" label="Not matched"/>
+  <int value="9" label="Empty URL"/>
 </enum>
 
 <enum name="UkmSyncDisableInfo">