dbus: Add ObjectProxy::EmptyResponseCallback().

This can be used when the caller is not interested in the response
from the D-bus method.

BUG=none
TEST=added a unit test


Review URL: http://codereview.chromium.org/8536007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@109598 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 42 insertions, 4 deletions

diff --git a/dbus/end_to_end_async_unittest.cc b/dbus/end_to_end_async_unittest.cc
index 7d52130..7ba782b 100644
--- a/dbus/end_to_end_async_unittest.cc
+++ b/dbus/end_to_end_async_unittest.cc
@@ -10,6 +10,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
+#include "base/test/test_timeouts.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "dbus/bus.h"
@@ -225,6 +226,28 @@ TEST_F(EndToEndAsyncTest, BrokenMethod) {
   ASSERT_EQ("", response_strings_[0]);
 }
 
+TEST_F(EndToEndAsyncTest, EmptyResponseCallback) {
+  const char* kHello = "hello";
+
+  // Create the method call.
+  dbus::MethodCall method_call("org.chromium.TestInterface", "Echo");
+  dbus::MessageWriter writer(&method_call);
+  writer.AppendString(kHello);
+
+  // Call the method with an empty callback.
+  const int timeout_ms = dbus::ObjectProxy::TIMEOUT_USE_DEFAULT;
+  object_proxy_->CallMethod(&method_call,
+                            timeout_ms,
+                            dbus::ObjectProxy::EmptyResponseCallback());
+  // Post a delayed task to quit the message loop.
+  message_loop_.PostDelayedTask(FROM_HERE,
+                                MessageLoop::QuitClosure(),
+                                TestTimeouts::tiny_timeout_ms());
+  message_loop_.Run();
+  // We cannot tell if the empty callback is called, but at least we can
+  // check if the test does not crash.
+}
+
 TEST_F(EndToEndAsyncTest, TestSignal) {
   const char kMessage[] = "hello, world";
   // Send the test signal from the exported object.
diff --git a/dbus/object_proxy.cc b/dbus/object_proxy.cc
index 1a3b7e0..d9a53d9 100644
--- a/dbus/object_proxy.cc
+++ b/dbus/object_proxy.cc
@@ -29,6 +29,10 @@ std::string GetAbsoluteSignalName(
   return interface_name + "." + signal_name;
 }
 
+// An empty function used for ObjectProxy::EmptyResponseCallback().
+void EmptyResponseCallbackBody(dbus::Response* unused_response) {
+}
+
 }  // namespace
 
 namespace dbus {
@@ -140,6 +144,11 @@ void ObjectProxy::Detach() {
   }
 }
 
+// static
+ObjectProxy::ResponseCallback ObjectProxy::EmptyResponseCallback() {
+  return base::Bind(&EmptyResponseCallbackBody);
+}
+
 ObjectProxy::OnPendingCallIsCompleteData::OnPendingCallIsCompleteData(
     ObjectProxy* in_object_proxy,
     ResponseCallback in_response_callback,
@@ -212,7 +221,7 @@ void ObjectProxy::RunResponseCallback(ResponseCallback response_callback,
                                       DBusMessage* response_message) {
   bus_->AssertOnOriginThread();
 
-  bool response_callback_called = false;
+  bool method_call_successful = false;
   if (!response_message) {
     // The response is not received.
     response_callback.Run(NULL);
@@ -235,14 +244,14 @@ void ObjectProxy::RunResponseCallback(ResponseCallback response_callback,
         dbus::Response::FromRawMessage(response_message));
     // The response is successfully received.
     response_callback.Run(response.get());
-    response_callback_called = true;
+    method_call_successful = true;
     // Record time spent for the method call. Don't include failures.
     UMA_HISTOGRAM_TIMES("DBus.AsyncMethodCallTime",
                         base::TimeTicks::Now() - start_time);
   }
   // Record if the method call is successful, or not. 1 if successful.
   UMA_HISTOGRAM_ENUMERATION("DBus.AsyncMethodCallSuccess",
-                            response_callback_called,
+                            method_call_successful,
                             kSuccessRatioHistogramMaxValue);
 }
 
diff --git a/dbus/object_proxy.h b/dbus/object_proxy.h
index 5fc4197..484f107 100644
--- a/dbus/object_proxy.h
+++ b/dbus/object_proxy.h
@@ -73,7 +73,9 @@ class ObjectProxy : public base::RefCountedThreadSafe<ObjectProxy> {
   // |callback| will be called in the origin thread, once the method call
   // is complete. As it's called in the origin thread, |callback| can
   // safely reference objects in the origin thread (i.e. UI thread in most
-  // cases).
+  // cases). If the caller is not interested in the response from the
+  // method (i.e. calling a method that does not return a value),
+  // EmptyResponseCallback() can be passed to the |callback| parameter.
   //
   // If the method call is successful, a pointer to Response object will
   // be passed to the callback. If unsuccessful, NULL will be passed to
@@ -106,6 +108,10 @@ class ObjectProxy : public base::RefCountedThreadSafe<ObjectProxy> {
   // BLOCKING CALL.
   virtual void Detach();
 
+  // Returns an empty callback that does nothing. Can be used for
+  // CallMethod().
+  static ResponseCallback EmptyResponseCallback();
+
  protected:
   // This is protected, so we can define sub classes.
   virtual ~ObjectProxy();