Only enumerate display_timing when present timestamp supported

Test: CTS and cube demo.
Bug: 36887025

Vulkan should only enumerate the VK_GOOGLE_display_timing extension if
the device supports reliably returning the present timestamp.  Vulkan
will determine this by reading a property that SurfaceFlinger will set
(based on the HWC2::Capability::PresentFenceIsNotReliable capability).

Change-Id: I6025be5f9120a8f02f228b8437b64be4ff8cfb17
diff --git a/vulkan/libvulkan/driver.cpp b/vulkan/libvulkan/driver.cpp
index 212d142..f2cd8e6 100644
--- a/vulkan/libvulkan/driver.cpp
+++ b/vulkan/libvulkan/driver.cpp
@@ -817,9 +817,6 @@
     loader_extensions.push_back({
         VK_KHR_INCREMENTAL_PRESENT_EXTENSION_NAME,
         VK_KHR_INCREMENTAL_PRESENT_SPEC_VERSION});
-    loader_extensions.push_back({
-        VK_GOOGLE_DISPLAY_TIMING_EXTENSION_NAME,
-        VK_GOOGLE_DISPLAY_TIMING_SPEC_VERSION});
 
     if (kEnableUnratifiedExtensions) {
         // conditionally add shared_presentable_image if supportable
@@ -832,6 +829,16 @@
         }
     }
 
+    // conditionally add VK_GOOGLE_display_timing if present timestamps are
+    // supported by the driver:
+    char timestamp_property[PROPERTY_VALUE_MAX];
+    property_get("service.sf.present_timestamp", timestamp_property, "1");
+    if (strcmp(timestamp_property, "1") == 0) {
+        loader_extensions.push_back({
+                VK_GOOGLE_DISPLAY_TIMING_EXTENSION_NAME,
+                VK_GOOGLE_DISPLAY_TIMING_SPEC_VERSION});
+    }
+
     // enumerate our extensions first
     if (!pLayerName && pProperties) {
         uint32_t count = std::min(