Some GrSemaphore cleanup

Remove unused GrResourceProvider functions that transfer context
ownership.

Return GrBackendSemaphore by value, make method public.

Change-Id: I1fe83b661cab82a54dde33b4b649579ea01be97c
Reviewed-on: https://skia-review.googlesource.com/150363
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
diff --git a/src/gpu/vk/GrVkSemaphore.cpp b/src/gpu/vk/GrVkSemaphore.cpp
index c794f7a..7a56391 100644
--- a/src/gpu/vk/GrVkSemaphore.cpp
+++ b/src/gpu/vk/GrVkSemaphore.cpp
@@ -63,7 +63,8 @@
     }
 }
 
-void GrVkSemaphore::setBackendSemaphore(GrBackendSemaphore* backendSemaphore) const {
-    backendSemaphore->initVulkan(fResource->semaphore());
+GrBackendSemaphore GrVkSemaphore::backendSemaphore() const {
+    GrBackendSemaphore backendSemaphore;
+    backendSemaphore.initVulkan(fResource->semaphore());
+    return backendSemaphore;
 }
-