[Chromecast] Adding correct SetDelegate method to MockGattClient

Currently, there is no way to set expectetions on SetDelegate function
Replaces with MOCK_METHOD1 and moving current function body to
ON_CALL().WillByDefault()

Bug: internal b/132811177

Change-Id: I58ba51d5a0d3dcead895045009de2821271ccfd4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1885453Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Luke Halliwell (slow) <halliwell@chromium.org>
Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Steven Zhu <jz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710978}

chromecast/device/bluetooth/shlib/mock_gatt_client.h

@@ -19,9 +19,7 @@ class MockGattClient : public GattClient {
   ~MockGattClient() override;
   MOCK_METHOD0(IsSupported, bool());
   MOCK_METHOD1(Connect, bool(const Addr&));
-  void SetDelegate(Gatt::Client::Delegate* delegate) override {
-    delegate_ = delegate;
-  }
+  MOCK_METHOD1(SetDelegate, void(Gatt::Client::Delegate*));
   MOCK_METHOD0(Enable, bool());
   MOCK_METHOD0(Disable, bool());
   MOCK_METHOD1(Disconnect, bool(const Addr&));
@@ -62,7 +60,11 @@ class MockGattClient : public GattClient {
   Gatt::Client::Delegate* delegate_ = nullptr;
 };
 
-inline MockGattClient::MockGattClient() = default;
+inline MockGattClient::MockGattClient() {
+  ON_CALL(*this, SetDelegate(::testing::_))
+      .WillByDefault(
+          [this](Gatt::Client::Delegate* delegate) { delegate_ = delegate; });
+}
 inline MockGattClient::~MockGattClient() = default;
 
 }  // namespace bluetooth_v2_shlib