Audio policy: fix device gain initialization

Fix initilization of default gain configuration for
audio devices loaded from audio_policy.conf.

Initialization cannot be done in constructor as the possible
gain configurations are not loaded yet.

Bug: 19120566.
Change-Id: I78f057ecfa1a121365ac3d8f317912a6f1647627
diff --git a/services/audiopolicy/AudioPolicyManager.cpp b/services/audiopolicy/AudioPolicyManager.cpp
index 0349327..fb74d66 100644
--- a/services/audiopolicy/AudioPolicyManager.cpp
+++ b/services/audiopolicy/AudioPolicyManager.cpp
@@ -7449,9 +7449,6 @@
                              NULL),
                      mDeviceType(type), mAddress(""), mId(0)
 {
-    if (mGains.size() > 0) {
-        mGains[0]->getDefaultConfig(&mGain);
-    }
 }
 
 bool AudioPolicyManager::DeviceDescriptor::equals(const sp<DeviceDescriptor>& other) const
@@ -7466,6 +7463,15 @@
                 mChannelMask == other->mChannelMask);
 }
 
+void AudioPolicyManager::DeviceDescriptor::loadGains(cnode *root)
+{
+    AudioPort::loadGains(root);
+    if (mGains.size() > 0) {
+        mGains[0]->getDefaultConfig(&mGain);
+    }
+}
+
+
 void AudioPolicyManager::DeviceVector::refreshTypes()
 {
     mDeviceTypes = AUDIO_DEVICE_NONE;