DtlsIdentityStoreInterface added and the implementation is called DtlsIdentityStoreImpl (previously named without the -Impl bit and without an interface).

DtlsIdentityStoreImpl is updated to take KeyType into account, something which will be relevant after this CL lands:
https://codereview.webrtc.org/1189583002

The DtlsIdentityService[Interface] classes are about to be removed (to be removed when Chromium no longer implements and uses the interface). This was an unnecessary layer of complexity. The FakeIdentityService is now instead a FakeDtlsIdentityStore.
Where a service was previously passed around, a store is now passed around.

Identity generation is now commonly performed using DtlsIdentityStoreInterface. Previously, if a service was not specified, WebRtcSessionDescriptionFactory could fall back on its own generation code. Now, a store has to be provided for generation to occur.

For more information about the steps being taken to land this without breaking Chromium, see referenced bug.

BUG=webrtc:4899
R=magjed@webrtc.org, tommi@webrtc.org

Review URL: https://codereview.webrtc.org/1176383004 .

Cr-Commit-Position: refs/heads/master@{#9696}
diff --git a/talk/app/webrtc/peerconnectioninterface_unittest.cc b/talk/app/webrtc/peerconnectioninterface_unittest.cc
index 9e68f5a..03ceaf2 100644
--- a/talk/app/webrtc/peerconnectioninterface_unittest.cc
+++ b/talk/app/webrtc/peerconnectioninterface_unittest.cc
@@ -32,7 +32,7 @@
 #include "talk/app/webrtc/mediastreaminterface.h"
 #include "talk/app/webrtc/peerconnectioninterface.h"
 #include "talk/app/webrtc/test/fakeconstraints.h"
-#include "talk/app/webrtc/test/fakedtlsidentityservice.h"
+#include "talk/app/webrtc/test/fakedtlsidentitystore.h"
 #include "talk/app/webrtc/test/mockpeerconnectionobservers.h"
 #include "talk/app/webrtc/test/testsdpstrings.h"
 #include "talk/app/webrtc/videosource.h"
@@ -264,17 +264,17 @@
           webrtc::MediaConstraintsInterface::kEnableDtlsSrtp, false);
     }
 
-    FakeIdentityService* dtls_service = NULL;
+    scoped_ptr<webrtc::DtlsIdentityStoreInterface> dtls_identity_store;
     bool dtls;
     if (FindConstraint(constraints,
                        webrtc::MediaConstraintsInterface::kEnableDtlsSrtp,
                        &dtls,
-                       NULL) && dtls) {
-      dtls_service = new FakeIdentityService();
+                       nullptr) && dtls) {
+      dtls_identity_store.reset(new FakeDtlsIdentityStore());
     }
     pc_ = pc_factory_->CreatePeerConnection(servers, constraints,
                                             port_allocator_factory_.get(),
-                                            dtls_service,
+                                            dtls_identity_store.Pass(),
                                             &observer_);
     ASSERT_TRUE(pc_.get() != NULL);
     observer_.SetPeerConnectionInterface(pc_.get());