[SH] Change the LinkOpenSource from boolean to enum histogram.

The histograms.xml already mentioned the enum.

Bug: 1138614
Change-Id: I6552185daf485e09ffe24063382f3b8f89433c7b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2473037Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: sebsg <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#817464}

third_party/blink/renderer/core/page/scrolling/text_fragment_anchor_metrics.cc

@@ -5,6 +5,7 @@
 #include "third_party/blink/renderer/core/page/scrolling/text_fragment_anchor_metrics.h"
 
 #include "base/check.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/time/default_tick_clock.h"
 #include "base/trace_event/trace_event.h"
@@ -182,8 +183,10 @@ void TextFragmentAnchorMetrics::ReportMetrics() {
                          time_to_scroll_into_view.InMilliseconds());
   }
 
-  UMA_HISTOGRAM_BOOLEAN("TextFragmentAnchor.LinkOpenSource",
-                        has_search_engine_source_);
+  base::UmaHistogramEnumeration("TextFragmentAnchor.LinkOpenSource",
+                                has_search_engine_source_
+                                    ? TextFragmentLinkOpenSource::kSearchEngine
+                                    : TextFragmentLinkOpenSource::kUnknown);
 #ifndef NDEBUG
   metrics_reported_ = true;
 #endif

third_party/blink/renderer/core/page/scrolling/text_fragment_anchor_metrics.h

@@ -40,6 +40,14 @@ class CORE_EXPORT TextFragmentAnchorMetrics final
     kMaxValue = kTextRangeWithContext,
   };
 
+  // Update corresponding |TextFragmentLinkOpenSource| in enums.xml.
+  enum class TextFragmentLinkOpenSource {
+    kUnknown,
+    kSearchEngine,
+
+    kMaxValue = kSearchEngine,
+  };
+
   explicit TextFragmentAnchorMetrics(Document* document);
 
   static TextFragmentAnchorParameters GetParametersForSelector(