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

ui/views/controls/textfield/textfield.h

 // Copyright (c) 2012 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 UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_H_
 #define UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 287 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,
@@ skipping 211 matching lines @@
 
   // Used to bind callback functions to this object.
   base::WeakPtrFactory<Textfield> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Textfield);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_H_