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

ui/views/controls/prefix_selector.cc

 // Copyright 2013 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.
 
 #include "ui/views/controls/prefix_selector.h"
 
 #include "base/i18n/case_conversion.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ime/text_input_type.h"
+#include "ui/display/display.h"
+#include "ui/display/screen.h"
 #include "ui/gfx/range/range.h"
 #include "ui/views/controls/prefix_delegate.h"
 #include "ui/views/view.h"
 #include "ui/views/widget/widget.h"
 
 namespace views {
 
 namespace {
 
 const int64_t kTimeBeforeClearingMS = 1000;
@@ skipping 50 matching lines @@
 }
 
 int PrefixSelector::GetTextInputFlags() const {
   return 0;
 }
 
 bool PrefixSelector::CanComposeInline() const {
   return false;
 }
 
+float PrefixSelector::GetScaleFactor() const {
+  return display::Screen::GetScreen()->GetDisplayNearestWindow(
+      host_view_->GetWidget()->GetNativeWindow()).device_scale_factor();
+}
+
 gfx::Rect PrefixSelector::GetCaretBounds() const {
   gfx::Rect rect(host_view_->GetVisibleBounds().origin(), gfx::Size());
   // TextInputClient::GetCaretBounds is expected to return a value in screen
   // coordinates.
   ConvertRectToScreen(host_view_, &rect);
   return rect;
 }
 
 bool PrefixSelector::GetCompositionCharacterBounds(uint32_t index,
                                                    gfx::Rect* rect) const {
@@ skipping 102 matching lines @@
   return (model_text.size() >= lower_text.size()) &&
       (model_text.compare(0, lower_text.size(), lower_text) == 0);
 }
 
 void PrefixSelector::ClearText() {
   current_text_.clear();
   time_of_last_key_ = base::TimeTicks();
 }
 
 }  // namespace views