Call addRef when creating a new Fence Sync object.

BUG=angle:728

Change-Id: Iafd838c3ceb1a88afd4d3b0994e8d841945df499
Reviewed-on: https://chromium-review.googlesource.com/213142
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
diff --git a/src/libGLESv2/ResourceManager.cpp b/src/libGLESv2/ResourceManager.cpp
index 3606532..701f2aa 100644
--- a/src/libGLESv2/ResourceManager.cpp
+++ b/src/libGLESv2/ResourceManager.cpp
@@ -151,7 +151,9 @@
 {
     GLuint handle = mFenceSyncHandleAllocator.allocate();
 
-    mFenceSyncMap[handle] = new FenceSync(mRenderer, handle);
+    FenceSync *fenceSync = new FenceSync(mRenderer, handle);
+    fenceSync->addRef();
+    mFenceSyncMap[handle] = fenceSync;
 
     return handle;
 }