[Passwords] Add self check to CPMC::OnPaste

This change adds a self check to ChromePasswordManagerClient::OnPaste
before dereferencing members.

Bug: 1161147
Change-Id: Ic36e5882d43bc3eae87c82e4d021cffca7ec8900
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2628950
Commit-Queue: Jan Wilken Dörrie <jdoerrie@chromium.org>
Reviewed-by: Friedrich [CET] <fhorschig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843613}

chrome/browser/password_manager/chrome_password_manager_client.cc

@@ -1316,6 +1316,12 @@ void ChromePasswordManagerClient::OnPaste() {
 
   base::string16 text;
   bool used_crosapi_workaround = false;
+
+  // Note: The call to `clipboard->ReadText()` below runs a nested message loop,
+  // potentially returning control back to this method after the client has been
+  // destroyed. Check `self` prior to dereferencing members.
+  base::WeakPtr<ChromePasswordManagerClient> self =
+      weak_ptr_factory_.GetWeakPtr();
 #if BUILDFLAG(IS_CHROMEOS_LACROS)
   // On Lacros, the ozone/wayland clipboard implementation is asynchronous by
   // default and runs a nested message loop to fake synchroncity. This in turn
@@ -1347,8 +1353,10 @@ void ChromePasswordManagerClient::OnPaste() {
     clipboard->ReadText(ui::ClipboardBuffer::kCopyPaste, &data_dst, &text);
   }
 
-  was_on_paste_called_ = true;
-  password_reuse_detection_manager_.OnPaste(std::move(text));
+  if (self) {
+    was_on_paste_called_ = true;
+    password_reuse_detection_manager_.OnPaste(std::move(text));
+  }
 }
 #endif
 

chrome/browser/password_manager/chrome_password_manager_client.h

@@ -12,6 +12,7 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/optional.h"
 #include "build/build_config.h"
 #include "build/chromeos_buildflags.h"
@@ -418,6 +419,11 @@ class ChromePasswordManagerClient
   // ChromePasswordManagerClient and IOSChromePasswordManagerClient.
   password_manager::PasswordManagerClientHelper helper_;
 
+  // This is added as a workaround for an issue inside OnPaste(). Please don't
+  // just use the WeakPtrs returned from this factory blindly, but make a
+  // informed decision after carefully considering the involved lifetimes.
+  base::WeakPtrFactory<ChromePasswordManagerClient> weak_ptr_factory_{this};
+
   WEB_CONTENTS_USER_DATA_KEY_DECL();
 
   DISALLOW_COPY_AND_ASSIGN(ChromePasswordManagerClient);