Adjust how present semaphore is handled

Avoids stashing a semaphore in a field
use unique_fd to ensure an unused present fence isn't leaked

Test: sample app ran in a loop for 3 hours, FD usage remained constant
Fixes: 295332012
Change-Id: Iee38e86587805ef3596e5f7efea3ca3b5c7758b3
diff --git a/libs/hwui/renderthread/VulkanManager.h b/libs/hwui/renderthread/VulkanManager.h
index dbef7fb..b92ebb3 100644
--- a/libs/hwui/renderthread/VulkanManager.h
+++ b/libs/hwui/renderthread/VulkanManager.h
@@ -22,6 +22,7 @@
 #endif
 #include <GrContextOptions.h>
 #include <SkSurface.h>
+#include <android-base/unique_fd.h>
 #include <utils/StrongPointer.h>
 #include <vk/GrVkBackendContext.h>
 #include <vk/GrVkExtensions.h>
@@ -82,10 +83,17 @@
     void destroySurface(VulkanSurface* surface);
 
     Frame dequeueNextBuffer(VulkanSurface* surface);
+
+    struct VkDrawResult {
+        // The estimated start time for intiating GPU work, -1 if unknown.
+        nsecs_t submissionTime;
+        android::base::unique_fd presentFence;
+    };
+
     // Finishes the frame and submits work to the GPU
-    // Returns the estimated start time for intiating GPU work, -1 otherwise.
-    nsecs_t finishFrame(SkSurface* surface);
-    void swapBuffers(VulkanSurface* surface, const SkRect& dirtyRect);
+    VkDrawResult finishFrame(SkSurface* surface);
+    void swapBuffers(VulkanSurface* surface, const SkRect& dirtyRect,
+                     android::base::unique_fd&& presentFence);
 
     // Inserts a wait on fence command into the Vulkan command buffer.
     status_t fenceWait(int fence, GrDirectContext* grContext);
@@ -201,9 +209,6 @@
     GrVkExtensions mExtensions;
     uint32_t mDriverVersion = 0;
 
-    VkSemaphore mSwapSemaphore = VK_NULL_HANDLE;
-    void* mDestroySemaphoreContext = nullptr;
-
     std::once_flag mInitFlag;
     std::atomic_bool mInitialized = false;
 };