Use the physical-pixel space for native IME on linux platform.

chrome/browser/ui/views/ime_driver/remote_text_input_client.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Reduce number of log messages by logging each NOTIMPLEMENTED() only once.
 // This has to be before any other includes, else default is picked up.
 // See base/logging.h for details on this.
 #define NOTIMPLEMENTED_POLICY 5
 
 #include "chrome/browser/ui/views/ime_driver/remote_text_input_client.h"
@@ skipping 51 matching lines @@
   return 0;
 }
 
 bool RemoteTextInputClient::CanComposeInline() const {
   // If we return false here, ui::InputMethodChromeOS will try to create a
   // composition window. But here we are at IMEDriver, and composition
   // window shouldn't be created by IMEDriver.
   return true;
 }
 
+float RemoteTextInputClient::GetScaleFactor() const {
+  return 1.0f;
+}
+
 gfx::Rect RemoteTextInputClient::GetCaretBounds() const {
   // TODO(moshayedi): crbug.com/631527.
   NOTIMPLEMENTED();
   return gfx::Rect();
 }
 
 bool RemoteTextInputClient::GetCompositionCharacterBounds(
     uint32_t index,
     gfx::Rect* rect) const {
   // TODO(moshayedi): crbug.com/631527.
@@ skipping 72 matching lines @@
   // TODO(moshayedi): crbug.com/631527.
   NOTIMPLEMENTED();
   return false;
 }
 
 void RemoteTextInputClient::SetTextEditCommandForNextKeyEvent(
     ui::TextEditCommand command) {
   // TODO(moshayedi): crbug.com/631527.
   NOTIMPLEMENTED();
 }