Fix rare crash in WebstoreInlineInstaller::CheckInlineInstallPermitted.

chrome/browser/extensions/webstore_inline_installer.cc

Index: chrome/browser/extensions/webstore_inline_installer.cc
diff --git a/chrome/browser/extensions/webstore_inline_installer.cc b/chrome/browser/extensions/webstore_inline_installer.cc
index 38931a3a35395b9415c522f708252523cc06b337..f58807993aab01e5fd7871c04dffdd0a0a385370 100644
--- a/chrome/browser/extensions/webstore_inline_installer.cc
+++ b/chrome/browser/extensions/webstore_inline_installer.cc
@@ -138,7 +138,8 @@ std::string WebstoreInlineInstaller::GetJsonPostData() {
 
 bool WebstoreInlineInstaller::CheckRequestorAlive() const {
   // The frame or tab may have gone away - cancel installation in that case.
-  return host_ != nullptr && web_contents() != nullptr;
+  return host_ != nullptr && web_contents() != nullptr &&
+         chrome::FindBrowserWithWebContents(web_contents()) != nullptr;
 }
 
 const GURL& WebstoreInlineInstaller::GetRequestorURL() const {