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

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

 // 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.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_IME_DRIVER_REMOTE_TEXT_INPUT_CLIENT_H_
 #define CHROME_BROWSER_UI_VIEWS_IME_DRIVER_REMOTE_TEXT_INPUT_CLIENT_H_
 
 #include "services/ui/public/interfaces/ime/ime.mojom.h"
 #include "ui/base/ime/text_input_client.h"
 
@@ skipping 10 matching lines @@
   void SetCompositionText(const ui::CompositionText& composition) override;
   void ConfirmCompositionText() override;
   void ClearCompositionText() override;
   void InsertText(const base::string16& text) override;
   void InsertChar(const ui::KeyEvent& event) override;
   ui::TextInputType GetTextInputType() const override;
   ui::TextInputMode GetTextInputMode() const override;
   base::i18n::TextDirection GetTextDirection() const override;
   int GetTextInputFlags() const override;
   bool CanComposeInline() const override;
+  float GetScaleFactor() const override;
   gfx::Rect GetCaretBounds() const override;
   bool GetCompositionCharacterBounds(uint32_t index,
                                      gfx::Rect* rect) const override;
   bool HasCompositionText() const override;
   bool GetTextRange(gfx::Range* range) const override;
   bool GetCompositionTextRange(gfx::Range* range) const override;
   bool GetSelectionRange(gfx::Range* range) const override;
   bool SetSelectionRange(const gfx::Range& range) override;
   bool DeleteRange(const gfx::Range& range) override;
   bool GetTextFromRange(const gfx::Range& range,
                         base::string16* text) const override;
   void OnInputMethodChanged() override;
   bool ChangeTextDirectionAndLayoutAlignment(
       base::i18n::TextDirection direction) override;
   void ExtendSelectionAndDelete(size_t before, size_t after) override;
   void EnsureCaretNotInRect(const gfx::Rect& rect) override;
   bool IsTextEditCommandEnabled(ui::TextEditCommand command) const override;
   void SetTextEditCommandForNextKeyEvent(ui::TextEditCommand command) override;
 
   ui::mojom::TextInputClientPtr remote_client_;
 
   DISALLOW_COPY_AND_ASSIGN(RemoteTextInputClient);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_IME_DRIVER_REMOTE_TEXT_INPUT_CLIENT_H_