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

content/browser/renderer_host/render_widget_host_view_aura.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 CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 189 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 371 matching lines @@
   std::unique_ptr<RenderWidgetHostViewEventHandler> event_handler_;
 
   base::WeakPtrFactory<RenderWidgetHostViewAura> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewAura);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_AURA_H_