Introduce use counters for Blink specific editing event usage

Source/core/frame/UseCounter.h

Index: Source/core/frame/UseCounter.h
diff --git a/Source/core/frame/UseCounter.h b/Source/core/frame/UseCounter.h
index 3f39c6144ff87ec964fef3dae696f4d5eab02fb8..93a2ad855fc5139d2bdefaf836f0aafd687aa24d 100644
--- a/Source/core/frame/UseCounter.h
+++ b/Source/core/frame/UseCounter.h
@@ -438,6 +438,19 @@ public:
         MixedContentImage = 438,
         MixedContentMedia = 439,
         DocumentFonts = 440,
+        // Editing related Blink specific events.
+        TextInputEventOnInput = 441,
+        TextInputEventOnTextArea = 442,
+        TextInputEventOnContentEditable= 443,
+        TextInputEventOnNotNode = 444,
+        WebkitBeforeTextInsertedOnInput = 445,
+        WebkitBeforeTextInsertedOnTextArea = 446,
+        WebkitBeforeTextInsertedOnContentEditable = 447,
+        WebkitBeforeTextInsertedOnNotNode = 448,
+        WebkitEditableContentChangedOnInput = 449,
+        WebkitEditableContentChangedOnTextArea = 450,
+        WebkitEditableContentChangedOnContentEditable = 451,
+        WebkitEditableContentChangedOnNotNode = 452,
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.
         // Also, run update_use_counter_feature_enum.py in chromium/src/tools/metrics/histograms/