Require a WebContents for checkSpelling

Bug: 763885
Change-Id: Id02e0e5223d305f4d61f9054e28e309281154809
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079717Reviewed-by: Robert Sesek <rsesek@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745639}

chrome/browser/renderer_host/chrome_render_widget_host_view_mac_delegate.mm

@@ -196,13 +196,13 @@ using content::RenderViewHost;
 - (void)checkSpelling:(id)sender {
   content::WebContents* webContents = content::WebContents::FromRenderViewHost(
       RenderViewHost::From(_renderWidgetHost));
-  DCHECK(webContents && webContents->GetFocusedFrame());
-
-  mojo::Remote<spellcheck::mojom::SpellCheckPanel>
-      focused_spell_check_panel_client;
-  webContents->GetFocusedFrame()->GetRemoteInterfaces()->GetInterface(
-      focused_spell_check_panel_client.BindNewPipeAndPassReceiver());
-  focused_spell_check_panel_client->AdvanceToNextMisspelling();
+  if (webContents && webContents->GetFocusedFrame()) {
+    mojo::Remote<spellcheck::mojom::SpellCheckPanel>
+        focused_spell_check_panel_client;
+    webContents->GetFocusedFrame()->GetRemoteInterfaces()->GetInterface(
+        focused_spell_check_panel_client.BindNewPipeAndPassReceiver());
+    focused_spell_check_panel_client->AdvanceToNextMisspelling();
+  }
 }
 
 // This message is sent by the spelling panel whenever a word is ignored.