Allow Windows to use system Vsync if only one window is swapping

ui/gl/gl_context_egl.cc

Index: ui/gl/gl_context_egl.cc
diff --git a/ui/gl/gl_context_egl.cc b/ui/gl/gl_context_egl.cc
index 5dd1aaf58ce88ceed3c1a0ef61c2a8116f6488c9..076de98635788463d1bbf08f9bd6a8596cc65449 100644
--- a/ui/gl/gl_context_egl.cc
+++ b/ui/gl/gl_context_egl.cc
@@ -29,7 +29,8 @@ GLContextEGL::GLContextEGL(GLShareGroup* share_group)
       context_(NULL),
       display_(NULL),
       config_(NULL),
-      unbind_fbo_on_makecurrent_(false) {
+      unbind_fbo_on_makecurrent_(false),
+      swap_interval_(1) {
 }
 
 bool GLContextEGL::Initialize(
@@ -125,6 +126,8 @@ bool GLContextEGL::MakeCurrent(GLSurface* surface) {
     return false;
   }
 
+  surface->OnSetSwapInterval(swap_interval_);
+
   release_current.Cancel();
   return true;
 }
@@ -183,6 +186,9 @@ void GLContextEGL::OnSetSwapInterval(int interval) {
   if (!eglSwapInterval(display_, interval)) {
     LOG(ERROR) << "eglSwapInterval failed with error "
                << GetLastEGLErrorString();
+  } else {
+    swap_interval_ = interval;
+    GLSurface::GetCurrent()->OnSetSwapInterval(interval);
   }
 }