Add plumbing for upcoming setFrameRate() api

Add plumbing from the app to surface flinger for the
ANativeWindow_setFrameRate() and ASurfaceTransaction_setFrameRate() api
calls we'll be adding soon.

We don't do anything in surface flinger with this data yet.

Bug: 143912624

Test: Added a new test, SetFrameRateTest.
Change-Id: I1cab87f3ce5afca4591a39d8e7a42cb1e86a368f
diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index 5bba7d3..2e2d745 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -111,6 +111,7 @@
     mCurrentState.frameRateSelectionPriority = PRIORITY_UNSET;
     mCurrentState.metadata = args.metadata;
     mCurrentState.shadowRadius = 0.f;
+    mCurrentState.frameRate = 0.f;
 
     // drawing state & current state are identical
     mDrawingState = mCurrentState;
@@ -1221,6 +1222,22 @@
     return true;
 }
 
+bool Layer::setFrameRate(float frameRate) {
+    if (mCurrentState.frameRate == frameRate) {
+        return false;
+    }
+
+    mCurrentState.sequence++;
+    mCurrentState.frameRate = frameRate;
+    mCurrentState.modified = true;
+    setTransactionFlags(eTransactionNeeded);
+    return true;
+}
+
+float Layer::getFrameRate() const {
+    return getDrawingState().frameRate;
+}
+
 void Layer::deferTransactionUntil_legacy(const sp<Layer>& barrierLayer, uint64_t frameNumber) {
     ATRACE_CALL();
     mCurrentState.barrierLayer_legacy = barrierLayer;