[android_webview] Do not declare WebView visible on detaching from window.

android_webview/browser/browser_view_renderer.h

Index: android_webview/browser/browser_view_renderer.h
diff --git a/android_webview/browser/browser_view_renderer.h b/android_webview/browser/browser_view_renderer.h
index 24e22781e9dc79405df4f70509a05180ce235f28..721dbcb03b19d80c7324547c4ce681c3de458e4c 100644
--- a/android_webview/browser/browser_view_renderer.h
+++ b/android_webview/browser/browser_view_renderer.h
@@ -145,6 +145,8 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient,
     return compositor_;
   }
 
+  bool window_visible_for_tests() const { return window_visible_; }
+
  private:
   void SetTotalRootLayerScrollOffset(const gfx::Vector2dF& new_value_dip);
   bool CanOnDraw();
@@ -193,6 +195,7 @@ class BrowserViewRenderer : public content::SynchronousCompositorClient,
   bool view_visible_;
   bool window_visible_;  // Only applicable if |attached_to_window_| is true.
   bool attached_to_window_;
+  bool was_attached_;  // Whether the view was attached to window at least once.
   bool hardware_enabled_;
   float dip_scale_;
   float page_scale_factor_;