Remove SimpleBroker and instead use the production broker implementation in tests.

mojo/edk/test/multiprocess_test_helper.h

Index: mojo/edk/test/multiprocess_test_helper.h
diff --git a/mojo/edk/test/multiprocess_test_helper.h b/mojo/edk/test/multiprocess_test_helper.h
index 3ff8b85ad9aeb8cf4db841d9cfbc6815f1af3cb2..55fef7c73ad1fa80f36a2186839aa1d3f7dac9bd 100644
--- a/mojo/edk/test/multiprocess_test_helper.h
+++ b/mojo/edk/test/multiprocess_test_helper.h
@@ -21,6 +21,8 @@ class PlatformChannelPair;
 
 namespace test {
 
+extern const char kBrokerHandleSwitch[];
+
 class MultiprocessTestHelper {
  public:
   MultiprocessTestHelper();
@@ -60,8 +62,12 @@ class MultiprocessTestHelper {
   static ScopedPlatformHandle client_platform_handle;
 
  private:
+  // Used differently depending on the test.
   scoped_ptr<PlatformChannelPair> platform_channel_pair_;
 
+  // Used by the broker.
+  scoped_ptr<PlatformChannelPair> broker_platform_channel_pair_;
+
   // Valid after |StartChild()| and before |WaitForChildShutdown()|.
   base::Process test_child_;