Delete backspace-for-back RuntimeFeature.

third_party/WebKit/Source/core/input/KeyboardEventManager.cpp

Index: third_party/WebKit/Source/core/input/KeyboardEventManager.cpp
diff --git a/third_party/WebKit/Source/core/input/KeyboardEventManager.cpp b/third_party/WebKit/Source/core/input/KeyboardEventManager.cpp
index f718f62007d0ceea44bd78e1cf4d1c0bedf318a4..0c15738f439693e596f1bc2dec41a3a572ae27e3 100644
--- a/third_party/WebKit/Source/core/input/KeyboardEventManager.cpp
+++ b/third_party/WebKit/Source/core/input/KeyboardEventManager.cpp
@@ -300,8 +300,6 @@ void KeyboardEventManager::DefaultKeyboardEventHandler(
       return;
     if (event->key() == "Tab") {
       DefaultTabEventHandler(event);
-    } else if (event->key() == "Backspace") {
-      DefaultBackspaceEventHandler(event);
     } else if (event->key() == "Escape") {
       DefaultEscapeEventHandler(event);
     } else {
@@ -338,28 +336,6 @@ void KeyboardEventManager::DefaultSpaceEventHandler(
   }
 }
 
-void KeyboardEventManager::DefaultBackspaceEventHandler(KeyboardEvent* event) {
-  DCHECK_EQ(event->type(), EventTypeNames::keydown);
-
-  if (!RuntimeEnabledFeatures::BackspaceDefaultHandlerEnabled())
-    return;
-
-  if (event->ctrlKey() || event->metaKey() || event->altKey())
-    return;
-
-  if (!frame_->GetEditor().Behavior().ShouldNavigateBackOnBackspace())
-    return;
-  UseCounter::Count(frame_->GetDocument(), WebFeature::kBackspaceNavigatedBack);
-  if (frame_->GetPage()->GetChromeClient().HadFormInteraction()) {
-    UseCounter::Count(frame_->GetDocument(),
-                      WebFeature::kBackspaceNavigatedBackAfterFormInteraction);
-  }
-  bool handled_event = frame_->Loader().Client()->NavigateBackForward(
-      event->shiftKey() ? 1 : -1);
-  if (handled_event)
-    event->SetDefaultHandled();
-}
-
 void KeyboardEventManager::DefaultArrowEventHandler(
     KeyboardEvent* event,
     Node* possible_focused_node) {