Add callback to flush for knowing when gpu is finished work.

Bug: skia:8802
Change-Id: I093c2a4e879b635b169a849d9af3e9f7a3d84a88
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/207870
Commit-Queue: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 075ac00..a2ca3d1 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -244,18 +244,21 @@
     RETURN_IF_ABANDONED
 
     this->drawingManager()->flush(nullptr, SkSurface::BackendSurfaceAccess::kNoAccess,
-                                  kNone_GrFlushFlags, 0, nullptr);
+                                  kNone_GrFlushFlags, 0, nullptr, nullptr, nullptr);
 }
 
 GrSemaphoresSubmitted GrContext::flush(GrFlushFlags flags, int numSemaphores,
-                                       GrBackendSemaphore signalSemaphores[]) {
+                                       GrBackendSemaphore signalSemaphores[],
+                                       GrGpuFinishedProc finishedProc,
+                                       GrGpuFinishedContext finishedContext) {
     ASSERT_SINGLE_OWNER
     if (this->abandoned()) {
         return GrSemaphoresSubmitted::kNo;
     }
 
     return this->drawingManager()->flush(nullptr, SkSurface::BackendSurfaceAccess::kNoAccess,
-                                         flags, numSemaphores, signalSemaphores);
+                                         flags, numSemaphores, signalSemaphores, finishedProc,
+                                         finishedContext);
 }
 
 ////////////////////////////////////////////////////////////////////////////////