Fix LinkGenerationError enum in text_fragment_selector_generator.

Max value was not set to the right value. Also changed to enum class,
which would cause the previous situation to not compile.

Change-Id: I0476ae21eaac5c3ef52de5bb70af073548333564
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2459691Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: sebsg <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815215}

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

@@ -32,7 +32,7 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
       public blink::mojom::blink::TextFragmentSelectorProducer {
  public:
   // Update corresponding |LinkGenerationError| in enums.xml.
-  enum LinkGenerationError {
+  enum class LinkGenerationError {
     kIncorrectSelector,
     kNoRange,
     kNoContext,
@@ -40,7 +40,7 @@ class CORE_EXPORT TextFragmentSelectorGenerator final
     kContextLimitReached,
     kEmptySelection,
 
-    kMaxValue = kContextLimitReached
+    kMaxValue = kEmptySelection
   };
   explicit TextFragmentSelectorGenerator() = default;