Allow Chromium's DBus service ownership to be stealable

dbus/bus.h

Index: dbus/bus.h
diff --git a/dbus/bus.h b/dbus/bus.h
index 220ed78af86ca844853fa35ddbe59afea34209ed..0b24cfbb2106915de7d16cbf2e2a8a426c7780c7 100644
--- a/dbus/bus.h
+++ b/dbus/bus.h
@@ -168,6 +168,22 @@ class CHROME_DBUS_EXPORT Bus : public base::RefCountedThreadSafe<Bus> {
     SUPPRESS_ERRORS,
   };
 
+  // Specifies service ownership options.
+  //
+  // REQUIRE_PRIMARY indicates that you require primary ownership of the
+  // service name.
+  //
+  // ALLOW_REPLACEMENT indicates that you'll allow another connection to
+  // steal ownership of this service name from you.
+  //
+  // REQUIRE_PRIMARY_ALLOW_REPLACEMENT does the obvious.
+  enum ServiceOwnershipOptions {
+    REQUIRE_PRIMARY = (DBUS_NAME_FLAG_DO_NOT_QUEUE |
+                       DBUS_NAME_FLAG_REPLACE_EXISTING),
+    ALLOW_REPLACEMENT = DBUS_NAME_FLAG_ALLOW_REPLACEMENT,

[satorux1, 2013/07/26 00:50:12]

Don't we need DBUS_NAME_FLAG_DO_NOT_QUEUE for this? I think we rarely want to
wait in the queue.

That said, simply copying the libdbus constants would be more straightforward:

enum ServiceOwnershipOptions {
  ALLOW_REPLACEMENT = DBUS_NAME_FLAG_ALLOW_REPLACEMENT,
  REPLACE_EXISTING = DBUS_NAME_FLAG_REPLACE_EXISTING,
  DO_NOT_QUEUE = DBUS_NAME_FLAG_DO_NOT_QUEUE,
}

Then RequestOwnership() would take 'int options' which is an OR'ed value of
ServiceOwnershipOptions.

[Chris Masone, 2013/07/26 01:00:24]

I thought about doing that, but wasn't sure if it made sense to have callers be
OR'ing together enum values.  That only works when the values are 0x1, 0x2, 0x4
etc (which they are here), but that's sort of an implementation detail.  That
was why I went with these semantically higher-level enum's.  I'm not married to
this approach, though, if you think that the other way is better.

[satorux1, 2013/07/26 01:14:45]

That's a good point. I think ALLOW_REPLACEMENT alone won't be used in the
caller, so what about just providing the two options:

enum ServiceOwnershipOptions {
  REQUIRE_PRIMARY = (DBUS_NAME_FLAG_DO_NOT_QUEUE |
DBUS_NAME_FLAG_REPLACE_EXISTING),
  REQUIRE_PRIMARY_ALLOW_REPLACEMENT = (REQUIRE_PRIMARY |
DBUS_NAME_FLAG_ALLOW_REPLACEMENT)
}

This would suffice for now. We can switch to the OR-ed value approach if needed
at a later time.

[Chris Masone, 2013/07/26 17:37:24]

Done.

+    REQUIRE_PRIMARY_ALLOW_REPLACEMENT = REQUIRE_PRIMARY | ALLOW_REPLACEMENT,
+  };
+
   // Options used to create a Bus object.
   struct CHROME_DBUS_EXPORT Options {
     Options();
@@ -398,13 +414,15 @@ class CHROME_DBUS_EXPORT Bus : public base::RefCountedThreadSafe<Bus> {
   //
   // Must be called in the origin thread.
   virtual void RequestOwnership(const std::string& service_name,
+                                ServiceOwnershipOptions options,
                                 OnOwnershipCallback on_ownership_callback);
 
   // Requests the ownership of the given service name.
   // Returns true on success, or the the service name is already obtained.
   //
   // BLOCKING CALL.
-  virtual bool RequestOwnershipAndBlock(const std::string& service_name);
+  virtual bool RequestOwnershipAndBlock(const std::string& service_name,
+                                        ServiceOwnershipOptions options);
 
   // Releases the ownership of the given service name.
   // Returns true on success.
@@ -608,6 +626,7 @@ class CHROME_DBUS_EXPORT Bus : public base::RefCountedThreadSafe<Bus> {
 
   // Helper function used for RequestOwnership().
   void RequestOwnershipInternal(const std::string& service_name,
+                                ServiceOwnershipOptions options,
                                 OnOwnershipCallback on_ownership_callback);
 
   // Helper function used for GetServiceOwner().