Allow overriding WebUIFactory when test flag is set.

chrome/browser/ui/webui/chrome_web_ui_factory.cc

Index: chrome/browser/ui/webui/chrome_web_ui_factory.cc
diff --git a/chrome/browser/ui/webui/chrome_web_ui_factory.cc b/chrome/browser/ui/webui/chrome_web_ui_factory.cc
index 71931fa327f22e02321d9aedf49a32bbfd5f4943..f1409abb800dcec01000c48f3c77ce4bf5b287a2 100644
--- a/chrome/browser/ui/webui/chrome_web_ui_factory.cc
+++ b/chrome/browser/ui/webui/chrome_web_ui_factory.cc
@@ -27,6 +27,7 @@
 #include "chrome/browser/ui/webui/plugins_ui.h"
 #include "chrome/browser/ui/webui/print_preview_ui.h"
 #include "chrome/browser/ui/webui/sync_internals_ui.h"
+#include "chrome/browser/ui/webui/test_chrome_web_ui_factory.h"
 #include "chrome/browser/ui/webui/textfields_ui.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/extensions/extension_constants.h"
@@ -217,6 +218,18 @@ static WebUIFactoryFunction GetWebUIFactoryFunction(Profile* profile,
   return NULL;
 }
 
+// When the test-type switch is set, return a TestType object, which should be a
+// subclass of Type.
+template<typename Type, typename TestType>
+struct PossibleTestSingletonTraits : public DefaultSingletonTraits<Type> {

[Evan Stade, 2011/05/24 17:25:59]

explicitly state privacy level

[Lei Zhang (Do not use), 2011/05/24 18:00:06]

Do you need this template? Why can't you just do the following in GetInstance()
?

if (CommandLine::ForCurrentProcess()->HasSwitch(some_flag))
  return Singleton<TestChromeWebUIFactory>::get();
else
  return Singleton<ChromeWebUIFactory>::get();

[Sheridan Rawlins, 2011/05/24 20:17:22]

This doesn't play nicely with the privacy/friendship example usage in
base/memory/singleton.h (get is only allowed in the GetIntance of the particular
type.

On 2011/05/24 18:00:06, thestig wrote:

[Sheridan Rawlins, 2011/05/24 20:17:22]

As a derived struct of DefaultSingletonTraits, which is a struct, I'll leave
this a struct too, as we discussed (struct's default privacy level is public).

[Sheridan Rawlins, 2011/05/25 18:29:42]

As discussed in email thread, my main argument for doing it here in traits
instead of in GetInstance() is that the if condition will be done exactly once
(when the singleton doesn't exist) rather than with every call to GetInstance().
 While the time savings may be minimal, it is conceptually what I want.  I'll
add a comment.

On 2011/05/24 18:00:06, thestig wrote:

+  static Type* New() {
+    if (CommandLine::ForCurrentProcess()->HasSwitch(switches::kTestType))
+      return DefaultSingletonTraits<TestType>::New();
+    else
+      return DefaultSingletonTraits<Type>::New();
+  }
+};
+
 }  // namespace
 
 WebUI::TypeID ChromeWebUIFactory::GetWebUIType(Profile* profile,
@@ -286,7 +299,8 @@ void ChromeWebUIFactory::GetFaviconForURL(
 
 // static
 ChromeWebUIFactory* ChromeWebUIFactory::GetInstance() {
-  return Singleton<ChromeWebUIFactory>::get();
+  return Singleton<ChromeWebUIFactory, PossibleTestSingletonTraits<
+      ChromeWebUIFactory, TestChromeWebUIFactory> >::get();
 }
 
 ChromeWebUIFactory::ChromeWebUIFactory() {