chrome: Improve positioning of the "Find" widget (fixes #3461)

The "Find" widget will be excluded from regions near the edges of the window
that contain overlays, draggable regions or titlebar.

libcef/browser/browser_platform_delegate.h

@@ -286,6 +286,9 @@ class CefBrowserPlatformDelegate {
   // Create the platform-specific menu runner.
   virtual std::unique_ptr<CefMenuRunner> CreateMenuRunner();
 
+  // Optionally modify the bounding box for the Chrome Find bar.
+  virtual void UpdateFindBarBoundingBox(gfx::Rect* bounds) const;
+
   // Returns true if this delegate implements windowless rendering. May be
   // called on multiple threads.
   virtual bool IsWindowless() const;