Fix Pango font rendering with HiDPi displays on Linux.

ui/gfx/linux_font_delegate.h

Index: ui/gfx/linux_font_delegate.h
diff --git a/ui/gfx/linux_font_delegate.h b/ui/gfx/linux_font_delegate.h
index 3a8d7bb86dcb74376d80b16e7ee0d77f31118960..95460b3fa452ae4b6cbba3042188297485e8b7d2 100644
--- a/ui/gfx/linux_font_delegate.h
+++ b/ui/gfx/linux_font_delegate.h
@@ -28,7 +28,7 @@ class GFX_EXPORT LinuxFontDelegate {
   //
   // Can return NULL, in case no toolkit has been set. (For example, if we're
   // running with the "--ash" flag.)
-  static const LinuxFontDelegate* instance();
+  static LinuxFontDelegate* instance();
 
   // Returns the default font rendering settings.
   virtual FontRenderParams GetDefaultFontRenderParams() const = 0;
@@ -39,7 +39,7 @@ class GFX_EXPORT LinuxFontDelegate {
       std::string* family_out,
       int* size_pixels_out,
       int* style_out,
-      FontRenderParams* params_out) const = 0;
+      FontRenderParams* params_out) = 0;
 };
 
 }  // namespace gfx