[AChoreographer] Add const qualifiers for getFd().

Per API feedback the AChoreographer argument should be const.

Bug: 148954590
Test: builds
Change-Id: Ie95481992534b3f5f5c664709bff80b1c21f7d50
diff --git a/libs/gui/DisplayEventDispatcher.cpp b/libs/gui/DisplayEventDispatcher.cpp
index 8af1a1c..15f966d 100644
--- a/libs/gui/DisplayEventDispatcher.cpp
+++ b/libs/gui/DisplayEventDispatcher.cpp
@@ -104,7 +104,7 @@
     mConfigChangeFlag = configChangeFlag;
 }
 
-int DisplayEventDispatcher::getFd() {
+int DisplayEventDispatcher::getFd() const {
     return mReceiver.getFd();
 }
 
diff --git a/libs/gui/include/gui/DisplayEventDispatcher.h b/libs/gui/include/gui/DisplayEventDispatcher.h
index 679d572..fcdf6bf 100644
--- a/libs/gui/include/gui/DisplayEventDispatcher.h
+++ b/libs/gui/include/gui/DisplayEventDispatcher.h
@@ -32,7 +32,7 @@
     void dispose();
     status_t scheduleVsync();
     void toggleConfigEvents(ISurfaceComposer::ConfigChanged configChangeFlag);
-    int getFd();
+    int getFd() const;
     virtual int handleEvent(int receiveFd, int events, void* data);
 
 protected: