Linux: revive a mysteriously disabled test and add tests for the GNOME Keyring native backend.

chrome/browser/password_manager/native_backend_gnome_x.h

Index: chrome/browser/password_manager/native_backend_gnome_x.h
===================================================================
--- chrome/browser/password_manager/native_backend_gnome_x.h	(revision 92796)
+++ chrome/browser/password_manager/native_backend_gnome_x.h	(working copy)
@@ -6,6 +6,8 @@
 #define CHROME_BROWSER_PASSWORD_MANAGER_NATIVE_BACKEND_GNOME_X_H_
 #pragma once
 
+#include <gnome-keyring.h>
+
 #include <string>
 
 #include "base/basictypes.h"
@@ -19,8 +21,50 @@
 struct PasswordForm;
 }
 
+// Many of the gnome_keyring_* functions use variable arguments, which makes
+// them difficult if not impossible to truly wrap in C. Therefore, we use
+// appropriately-typed function pointers and scoping to make the fact that we
+// might be dynamically loading the library almost invisible. As a bonus, we
+// also get a simple way to mock the library for testing. Classes that inherit
+// from GnomeKeyringLoader will use its versions of the gnome_keyring_*
+// functions. Note that it has only static fields.
+class GnomeKeyringLoader {
+ protected:
+  static bool LoadGnomeKeyring();
+
+// Call a given parameter with the name of each function we use from GNOME
+// Keyring. Make sure to adjust the unit test if you change these.
+#define GNOME_KEYRING_FOR_EACH_FUNC(F)          \
+  F(is_available)                               \
+  F(store_password)                             \
+  F(delete_password)                            \
+  F(find_itemsv)                                \
+  F(result_to_message)
+
+// Declare the actual function pointers that we'll use in client code.
+#define GNOME_KEYRING_DECLARE_POINTER(name) \
+    static typeof(&::gnome_keyring_##name) gnome_keyring_##name;
+  GNOME_KEYRING_FOR_EACH_FUNC(GNOME_KEYRING_DECLARE_POINTER)
+#undef GNOME_KEYRING_DECLARE_POINTER
+
+  // Set to true if LoadGnomeKeyring() has already succeeded.
+  static bool keyring_loaded;
+
+ private:
+#if defined(DLOPEN_GNOME_KEYRING)
+  struct FunctionInfo {
+    const char* name;
+    void** pointer;
+  };
+
+  // Make it easy to initialize the function pointers in LoadGnomeKeyring().
+  static const FunctionInfo functions[];

[Evan Martin, 2011/07/18 15:31:00]

I'm surprised this is legal -- you'd think the array is inline so the compiler
needs to know the size of the array in the header.  Maybe we're saved because
it's static?  No worries.

[Mike Mammarella, 2011/07/19 00:20:35]

Yes, static is what saves us. Would you be as surprised if I'd written static
const char kSomeConstString[]; ?

+#endif  // !defined(DLOPEN_GNOME_KEYRING)
+};
+
 // NativeBackend implementation using GNOME Keyring.
-class NativeBackendGnome : public PasswordStoreX::NativeBackend {
+class NativeBackendGnome : public PasswordStoreX::NativeBackend,
+                           public GnomeKeyringLoader {

[Evan Martin, 2011/07/18 15:31:00]

This is weird.  The class is all statics, right?  So it's just for namespacing? 
Why do we need this?

[Mike Mammarella, 2011/07/19 00:20:35]

The comment above explains this somewhat; is it not sufficiently clear?
Basically this is a name resolution ordering trick to get rid of the
preprocessor macros #define gnome_keyring_foo wrap_gnome_keyring_foo

  public:
   NativeBackendGnome(LocalProfileId id, PrefService* prefs);