[Sh-Blink] Return invalid selector when no match found.

When TextFragmentFinder finds no match for the provided selector,
TextFragmentSelectorGenerator should be notified so that it notifies the
user that generation failed.
As selector provided by TextFragmentSelectorGenerator is constructed for
the selection from the user, this can happen only if selector is
incorrectly constructed.

Bug: 1129649
Change-Id: I10b5a49602128b532166a66354faa905493fb7f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2426464
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811006}

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

@@ -84,6 +84,8 @@ class CORE_EXPORT TextFragmentAnchor final : public FragmentAnchor,
                     const TextFragmentAnchorMetrics::Match match_metrics,
                     bool is_unique) override;
 
+  void NoMatchFound() override {}
+
  private:
   // Called when the search is finished. Reports metrics and activates the
   // element fragment anchor if we didn't find a match.

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

@@ -240,6 +240,8 @@ void TextFragmentFinder::FindMatch(Document& document) {
     EphemeralRangeInFlatTree ambiguous_match =
         FindMatchFromPosition(document, match.EndPosition());
     client_.DidFindMatch(match, match_metrics, ambiguous_match.IsNull());
+  } else {
+    client_.NoMatchFound();
   }
 }
 

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

@@ -26,6 +26,7 @@ class CORE_EXPORT TextFragmentFinder final {
         const EphemeralRangeInFlatTree& range,
         const TextFragmentAnchorMetrics::Match match_metrics,
         bool is_unique) = 0;
+    virtual void NoMatchFound() = 0;
   };
 
   // Client must outlive the finder.

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

@@ -289,6 +289,11 @@ void TextFragmentSelectorGenerator::DidFindMatch(
   }
 }
 
+void TextFragmentSelectorGenerator::NoMatchFound() {
+  NotifySelectorReady(
+      TextFragmentSelector(TextFragmentSelector::SelectorType::kInvalid));
+}
+
 void TextFragmentSelectorGenerator::NotifySelectorReady(
     const TextFragmentSelector& selector) {
   DCHECK(pending_generate_selector_callback_);

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

@@ -53,6 +53,8 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
                     const TextFragmentAnchorMetrics::Match match_metrics,
                     bool is_unique) override;
 
+  void NoMatchFound() override;
+
   // Notifies the results of |GenerateSelector|.
   void NotifySelectorReady(const TextFragmentSelector& selector);