Remove RenderViewObserver::Resized (try 2)

The only client was AutofillAgent; reimplement the functionality in a slightly different way. While we're at it, fix a bug where the browser-owned popup is hidden without the renderer's knowledge.

BUG=433486,449325

Review URL: https://codereview.chromium.org/854943002

Cr-Commit-Position: refs/heads/master@{#312346}
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index 0f56ad43..5db6b0d 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -535,6 +535,8 @@
 
   void RenderWidgetDeleted(RenderWidgetHostImpl* render_widget_host) override;
   void RenderWidgetGotFocus(RenderWidgetHostImpl* render_widget_host) override;
+  void RenderWidgetWasResized(
+      RenderWidgetHostImpl* render_widget_host) override;
   bool PreHandleKeyboardEvent(const NativeWebKeyboardEvent& event,
                               bool* is_keyboard_shortcut) override;
   void HandleKeyboardEvent(const NativeWebKeyboardEvent& event) override;