Add flag to enable rendering of text using signed distance fields.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 5695270eba31e26b25a34ca4c828a8bf6341caef..eb84806d9a7bf458f3580c075b1a5ce7614bf854 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -216,6 +216,10 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
 
   bool is_lcd_text_enabled() const { return is_lcd_text_enabled_; }
 
+  bool is_distance_field_text_enabled() const {
+    return is_distance_field_text_enabled_;
+  }
+
   bool is_zero_copy_enabled() const { return is_zero_copy_enabled_; }
 
   bool is_one_copy_enabled() const { return is_one_copy_enabled_; }
@@ -545,6 +549,7 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
   bool is_impl_side_painting_enabled_;
   bool is_low_res_tiling_enabled_;
   bool is_lcd_text_enabled_;
+  bool is_distance_field_text_enabled_;
   bool is_zero_copy_enabled_;
   bool is_one_copy_enabled_;