Fix Crash in Hung Pages view while in screen reader

There seems to be a timing issue between the AX queries for
GetText and when the model is updating. Looking at the model
it seems not all TabDestroyed calls are informing the Observers
that the model has changed.

The TableView uses Virtual AX Children that depends on the
observers to call. Moved the observer call from TabDestroyed to Reset
to handle all delegate_->TabDestroyed() calls defined below:

 - RenderProcessExited
 - RenderWidgetHostDestroyed
 - TabDestroyed,
 - RenderViewHostChanged
 - WebContentsDestroyed

Bug: 1140454
Change-Id: Ie7fd07d6540b9509b998d5cd95d1fd16f47f9018
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2530295Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Mohamed Mansour <mmansour@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#827900}

chrome/browser/ui/views/hung_renderer_view.cc

@@ -106,6 +106,10 @@ void HungPagesTableModel::Reset() {
   widget_observer_.RemoveAll();
   tab_observers_.clear();
   render_widget_host_ = nullptr;
+
+  // Inform the table model observers that we cleared the model.
+  if (observer_)
+    observer_->OnModelChanged();
 }
 
 void HungPagesTableModel::RestartHangMonitorTimeout() {

chrome/browser/ui/views/hung_renderer_view.h

@@ -155,6 +155,8 @@ class HungRendererDialogView : public views::DialogDelegateView,
   // Returns true if the frame is in the foreground.
   static bool IsFrameActive(content::WebContents* contents);
 
+  views::TableView* table_for_testing() { return hung_pages_table_; }
+
   virtual void ShowForWebContents(
       content::WebContents* contents,
       content::RenderWidgetHost* render_widget_host,

chrome/browser/ui/views/hung_renderer_view_browsertest.cc

@@ -21,6 +21,7 @@
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/test/browser_test.h"
 #include "content/public/test/browser_test_utils.h"
+#include "ui/views/accessibility/view_accessibility.h"
 
 // Interactive UI tests for the hung renderer (aka page unresponsive) dialog.
 class HungRendererDialogViewBrowserTest : public DialogBrowserTest {
@@ -77,7 +78,7 @@ IN_PROC_BROWSER_TEST_F(HungRendererDialogViewBrowserTest, InactiveWindow) {
   // This is what happens when HungRendererDialogView::ShowForWebContents
   // returns early if the frame or the dialog are not active.
   HungRendererDialogView::Create(browser()->window()->GetNativeWindow());
-  EXPECT_TRUE(HungRendererDialogView::GetInstance());
+  ASSERT_TRUE(HungRendererDialogView::GetInstance());
 
   // Simulate the renderer becoming responsive again.
   content::WebContents* web_contents =
@@ -87,3 +88,27 @@ IN_PROC_BROWSER_TEST_F(HungRendererDialogViewBrowserTest, InactiveWindow) {
   content::WebContentsDelegate* web_contents_delegate = browser();
   web_contents_delegate->RendererResponsive(web_contents, render_widget_host);
 }
+
+IN_PROC_BROWSER_TEST_F(HungRendererDialogViewBrowserTest, ProcessClosed) {
+  HungRendererDialogView* dialog =
+      HungRendererDialogView::Create(browser()->window()->GetNativeWindow());
+  ASSERT_TRUE(dialog);
+
+  auto* web_contents = browser()->tab_strip_model()->GetActiveWebContents();
+  dialog->ShowForWebContents(
+      web_contents,
+      web_contents->GetMainFrame()->GetRenderViewHost()->GetWidget(),
+      base::DoNothing::Repeatedly());
+
+  views::ViewAccessibility& view_accessibility =
+      dialog->table_for_testing()->GetViewAccessibility();
+  EXPECT_EQ(size_t{1}, view_accessibility.virtual_children().size());
+
+  // Simulate an abrupt ending to webcontents. The accessibility tree for the
+  // TableView depends on the Hung Render View table model to send the right
+  // events. By checking the virtual tree, we can guarantee the sync is correct.
+  dialog->EndForWebContents(
+      web_contents,
+      web_contents->GetMainFrame()->GetRenderViewHost()->GetWidget());
+  EXPECT_EQ(size_t{0}, view_accessibility.virtual_children().size());
+}