Remove print stack trace on keyboard controller error.

debug: :StackTrace is used in line 664.
Change-Id: If061f891d3ef4454aad07fc3135d93830ee781db
Reviewed-on: https://chromium-review.googlesource.com/740261
Commit-Queue: Siddhartha S <ssid@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Reviewed-by: Keigo Oka <oka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512446}

ui/keyboard/keyboard_controller.cc

@@ -687,8 +687,7 @@ void KeyboardController::CheckStateTransition(KeyboardControllerState prev,
 
   DCHECK(error_message.str().empty())
       << "State: " << StateToStr(prev) << " -> " << StateToStr(next) << " "
-      << error_message.str()
-      << "  stack trace: " << base::debug::StackTrace(10).ToString();
+      << error_message.str();
 }
 
 void KeyboardController::ChangeState(KeyboardControllerState state) {