Select-to-Speak's event handler should only be called when STS is enabled.

Changes a "if" to a "DCHECK".

Change-Id: I17cbe0efee059bbc76ca85cacd395f57b1ac41a2
Reviewed-on: https://chromium-review.googlesource.com/1178224Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583812}

chrome/browser/chromeos/accessibility/select_to_speak_event_handler.cc

@@ -92,9 +92,7 @@ bool SelectToSpeakEventHandler::IsSelectToSpeakEnabled() {
 }
 
 void SelectToSpeakEventHandler::OnKeyEvent(ui::KeyEvent* event) {
-  if (!IsSelectToSpeakEnabled())
-    return;
-
+  DCHECK(IsSelectToSpeakEnabled());
   DCHECK(event);
 
   // We can only call TtsController on the UI thread, make sure we
@@ -163,9 +161,7 @@ void SelectToSpeakEventHandler::OnKeyEvent(ui::KeyEvent* event) {
 }
 
 void SelectToSpeakEventHandler::OnMouseEvent(ui::MouseEvent* event) {
-  if (!IsSelectToSpeakEnabled())
-    return;
-
+  DCHECK(IsSelectToSpeakEnabled());
   DCHECK(event);
   if (state_ == INACTIVE) {
     if (event->type() == ui::ET_MOUSE_PRESSED) {
@@ -209,9 +205,7 @@ void SelectToSpeakEventHandler::OnMouseEvent(ui::MouseEvent* event) {
 }
 
 void SelectToSpeakEventHandler::OnTouchEvent(ui::TouchEvent* event) {
-  if (!IsSelectToSpeakEnabled())
-    return;
-
+  DCHECK(IsSelectToSpeakEnabled());
   DCHECK(event);
 
   if (state_ == INACTIVE && event->type() == ui::ET_TOUCH_PRESSED) {