Fix DCHECK in debug build when navigating to an unknown chrome://theme/ URL.

chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc

Index: chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc
diff --git a/chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc b/chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc
index 78ffc3226fe4942b391eb4eca82d348e638988c2..0343abce9ad7f36da79694e6f0a5fd41e5f3d9a8 100644
--- a/chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc
+++ b/chrome/browser/ui/webui/chrome_url_data_manager_browsertest.cc
@@ -3,10 +3,13 @@
 // found in the LICENSE file.
 
 #include "base/macros.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/navigation_details.h"
+#include "content/public/browser/navigation_handle.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_source.h"
@@ -44,6 +47,34 @@ class NavigationNotificationObserver : public content::NotificationObserver {
   DISALLOW_COPY_AND_ASSIGN(NavigationNotificationObserver);
 };
 
+class NavigationObserver : public content::WebContentsObserver {
+public:
+  enum NavigationResult {
+    NOT_FINISHED,
+    ERROR_PAGE,
+    SUCCESS,
+  };
+
+  explicit NavigationObserver(content::WebContents* web_contents)
+      : WebContentsObserver(web_contents), navigation_result_(NOT_FINISHED) {}
+  ~NavigationObserver() override = default;
+
+  void DidFinishNavigation(
+      content::NavigationHandle* navigation_handle) override {
+    navigation_result_ =
+        navigation_handle->IsErrorPage() ? ERROR_PAGE : SUCCESS;
+  }
+
+  NavigationResult navigation_result() const { return navigation_result_; }
+
+  void Reset() { navigation_result_ = NOT_FINISHED; }
+
+ private:
+  NavigationResult navigation_result_;
+
+  DISALLOW_COPY_AND_ASSIGN(NavigationObserver);
+};
+
 }  // namespace
 
 typedef InProcessBrowserTest ChromeURLDataManagerTest;
@@ -57,11 +88,34 @@ IN_PROC_BROWSER_TEST_F(ChromeURLDataManagerTest, 200) {
   EXPECT_EQ(200, observer.http_status_code());
 }
 
+// Makes sure browser does not crash when navigating to an unknown resource.
+IN_PROC_BROWSER_TEST_F(ChromeURLDataManagerTest, UnknownResource) {
+  // Known resource
+  NavigationObserver observer(
+      browser()->tab_strip_model()->GetActiveWebContents());
+  ui_test_utils::NavigateToURL(
+      browser(), GURL("chrome://theme/IDR_SETTINGS_FAVICON"));
+  EXPECT_EQ(NavigationObserver::SUCCESS, observer.navigation_result());
+
+  // Unknown resource
+  observer.Reset();
+  ui_test_utils::NavigateToURL(
+      browser(), GURL("chrome://theme/IDR_ASDFGHJKL"));
+  EXPECT_EQ(NavigationObserver::ERROR_PAGE, observer.navigation_result());
+}
+
 // Makes sure browser does not crash when the resource scale is very large.
-IN_PROC_BROWSER_TEST_F(ChromeURLDataManagerTest, ResourceScaleTest) {
+IN_PROC_BROWSER_TEST_F(ChromeURLDataManagerTest, LargeResourceScale) {
+  // Valid scale
+  NavigationObserver observer(
+      browser()->tab_strip_model()->GetActiveWebContents());
   ui_test_utils::NavigateToURL(
       browser(), GURL("chrome://theme/IDR_SETTINGS_FAVICON@2x"));
+  EXPECT_EQ(NavigationObserver::SUCCESS, observer.navigation_result());
 
+  // Unreasonably large scale
+  observer.Reset();
   ui_test_utils::NavigateToURL(
       browser(), GURL("chrome://theme/IDR_SETTINGS_FAVICON@99999x"));
+  EXPECT_EQ(NavigationObserver::SUCCESS, observer.navigation_result());
 }