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

ui/base/ime/dummy_text_input_client.cc

Index: ui/base/ime/dummy_text_input_client.cc
diff --git a/ui/base/ime/dummy_text_input_client.cc b/ui/base/ime/dummy_text_input_client.cc
index 60ae481d1271b00dbbf923076471778687ea565e..a857b87c1567508731fd246222d96b0844e71edf 100644
--- a/ui/base/ime/dummy_text_input_client.cc
+++ b/ui/base/ime/dummy_text_input_client.cc
@@ -65,6 +65,10 @@ bool DummyTextInputClient::CanComposeInline() const {
   return false;
 }
 
+float DummyTextInputClient::GetScaleFactor() const {
+  return 1.0f;
+}
+
 gfx::Rect DummyTextInputClient::GetCaretBounds() const {
   return gfx::Rect();
 }