SurfaceFlinger: Add DISPLAY_EVENT_FRAME_RATE_OVERRIDE

Add a new event to DisplayEventReceiver that conveys a list
of apps whose frame rates have been overriden.
This event is processed by the DisplayManager to advertise the
new frame rate to the overridden app.

Change-Id: I89fce8b5b4d9db65ec5db7dd2393c384c0fcfd82
Bug: 169271059
Bug: 169271062
Bug: 170503758
Test: manual test using SF backdoor
diff --git a/libs/gui/tests/Surface_test.cpp b/libs/gui/tests/Surface_test.cpp
index 2392ae5..ce3afa2 100644
--- a/libs/gui/tests/Surface_test.cpp
+++ b/libs/gui/tests/Surface_test.cpp
@@ -687,7 +687,7 @@
 
     sp<ISurfaceComposerClient> createConnection() override { return nullptr; }
     sp<IDisplayEventConnection> createDisplayEventConnection(
-            ISurfaceComposer::VsyncSource, ISurfaceComposer::ConfigChanged) override {
+            ISurfaceComposer::VsyncSource, ISurfaceComposer::EventRegistrationFlags) override {
         return nullptr;
     }
     sp<IBinder> createDisplay(const String8& /*displayName*/,