Add WebUI::GetDeviceScale

content/public/browser/web_ui.h

Index: content/public/browser/web_ui.h
diff --git a/content/public/browser/web_ui.h b/content/public/browser/web_ui.h
index 8bb0734d86dc5d917d8a3badd11ad36c0015c475..b0d8a08531630b9afb4a86d7d16ac4a36416593f 100644
--- a/content/public/browser/web_ui.h
+++ b/content/public/browser/web_ui.h
@@ -52,6 +52,11 @@ class CONTENT_EXPORT WebUI {
   virtual WebUIController* GetController() const = 0;
   virtual void SetController(WebUIController* controller) = 0;
 
+  // Returns the device scale of the monitor that the renderer is on.
+  // Whenever possible, WebUI should push resources with this scale to
+  // Javascript.
+  virtual float GetDeviceScale() const = 0;
+
   // Returns true if the favicon should be hidden for the current tab.
   virtual bool ShouldHideFavicon() const = 0;
   virtual void HideFavicon() = 0;