Revert "SF: Remove refresh_rate_switching flag."

This reverts commit 8c6f3f6bd0c5edce7aa9bfd61b64dd2e7dc43deb.

Reason for revert: Crashes on ToT (b/148822765, b/148821456)

Change-Id: If1bc13b33321727244c3b0f15a0e7b30665d1c43
diff --git a/services/surfaceflinger/SurfaceFlingerProperties.cpp b/services/surfaceflinger/SurfaceFlingerProperties.cpp
index 768074a..b4716eb 100644
--- a/services/surfaceflinger/SurfaceFlingerProperties.cpp
+++ b/services/surfaceflinger/SurfaceFlingerProperties.cpp
@@ -226,6 +226,14 @@
     return static_cast<int64_t>(defaultValue);
 }
 
+bool refresh_rate_switching(bool defaultValue) {
+    auto temp = SurfaceFlingerProperties::refresh_rate_switching();
+    if (temp.has_value()) {
+        return *temp;
+    }
+    return defaultValue;
+}
+
 int32_t set_idle_timer_ms(int32_t defaultValue) {
     auto temp = SurfaceFlingerProperties::set_idle_timer_ms();
     if (temp.has_value()) {