Do not save passwords after back-navigation

chrome/browser/password_manager/password_manager_browsertest.cc

Index: chrome/browser/password_manager/password_manager_browsertest.cc
diff --git a/chrome/browser/password_manager/password_manager_browsertest.cc b/chrome/browser/password_manager/password_manager_browsertest.cc
index 63ad1204d1807210ca3033a0868c8bb3ea3311f5..d4243ffccb2453f8def23e8ab1d0d1b62d3d20d2 100644
--- a/chrome/browser/password_manager/password_manager_browsertest.cc
+++ b/chrome/browser/password_manager/password_manager_browsertest.cc
@@ -1583,3 +1583,35 @@ IN_PROC_BROWSER_TEST_F(PasswordManagerBrowserTest,
   observer.Wait();
   EXPECT_FALSE(prompt_observer->IsShowingPrompt());
 }
+
+IN_PROC_BROWSER_TEST_F(PasswordManagerBrowserTest, NoPromptOnBack) {
+  // Go to a successful landing page through submitting first, so that it is
+  // reachable through going back, and the remembered page transition is form
+  // submit. There is no need to submit non-empty strings.
+  NavigateToFile("/password/password_form.html");
+
+  NavigationObserver dummy_submit_observer(WebContents());
+  std::string just_submit =
+      "document.getElementById('input_submit_button').click()";
+  ASSERT_TRUE(content::ExecuteScript(RenderViewHost(), just_submit));
+  dummy_submit_observer.Wait();
+
+  // Now go to a page with a form again, fill the form, and go back instead of
+  // submitting it.
+  NavigateToFile("/password/dummy_submit.html");
+
+  NavigationObserver observer(WebContents());
+  scoped_ptr<PromptObserver> prompt_observer(
+      PromptObserver::Create(WebContents()));
+  // The (dummy) submit is necessary to provisionally save the typed password. A
+  // user typing in the password field would not need to submit to provisionally
+  // save it, but the script cannot trigger that just by assigning to the
+  // field's value.
+  std::string fill_and_back =
+      "document.getElementById('password_field').value = 'random';"
+      "document.getElementById('input_submit_button').click();"
+      "window.history.back();";
+  ASSERT_TRUE(content::ExecuteScript(RenderViewHost(), fill_and_back));
+  observer.Wait();
+  EXPECT_FALSE(prompt_observer->IsShowingPrompt());
+}