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

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 6b880fadd32008ee2935fb01990215f6d21e67a8..635b44c55eb27d8a5b4f9c628e67ef70807a2de1 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -207,6 +207,7 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   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;