Update foveation default settings to 'medium' for Quest compatibility

runtime/include/runtime_config.h

@@ -261,8 +261,12 @@ inline bool IsSupportedVrPerformanceLevel(std::string_view value) {
 // 4x4 pixel blocks, the higher the level the closer to the centre. Whether the
 // GPU device gets fragment density maps at all is decided at launch, so going
 // from "off" to a level takes a restart; between levels and back to "off" it is
-// live.
+// live. The Quest starts at "medium"; elsewhere it does nothing.
+#if defined(__ANDROID__)
+inline constexpr const char* kVrFoveationDefault = "medium";
+#else
 inline constexpr const char* kVrFoveationDefault = "off";
+#endif
 inline constexpr std::array<std::string_view, 4> kVrFoveationLevels{"off", "low", "medium", "high"};
 
 inline bool IsSupportedVrFoveation(std::string_view value) {

runtime/tests/vr_config_tests.cpp

@@ -23,7 +23,11 @@ int main() {
     Require(!Parse("[vr]\nfoveation = \"ultra\"\n").vrFoveation.has_value());
     Require(!Parse("[vr]\nfoveation = 2\n").vrFoveation.has_value());
     Require(!Parse("[vr]\n").vrFoveation.has_value());
+#if defined(__ANDROID__)
+    Require(std::string_view(RuntimeConfigFile::kVrFoveationDefault) == "medium");
+#else
     Require(std::string_view(RuntimeConfigFile::kVrFoveationDefault) == "off");
+#endif
     Require(RuntimeConfigFile::VrFoveationLevelIndex("off") == 0);
     Require(RuntimeConfigFile::VrFoveationLevelIndex("low") == 1);
     Require(RuntimeConfigFile::VrFoveationLevelIndex("medium") == 2);