Do glFinish before sending snapshot latency info to browser

ui/gl/gl_surface.cc

Index: ui/gl/gl_surface.cc
diff --git a/ui/gl/gl_surface.cc b/ui/gl/gl_surface.cc
index f16d498340905e6ea1496b9b9f4d192d97aaa449..f89a699c807be96f4d57f43d2eb8f8180e15d2ac 100644
--- a/ui/gl/gl_surface.cc
+++ b/ui/gl/gl_surface.cc
@@ -190,6 +190,10 @@ gfx::Vector2d GLSurface::GetDrawOffset() const {
   return gfx::Vector2d();
 }
 
+void GLSurface::WaitForSnapshotRendering() {
+  // By default, just executing the SwapBuffers is normally enough.
+}
+
 GLSurface* GLSurface::GetCurrent() {
   return current_surface_.Pointer()->Get();
 }
@@ -389,6 +393,10 @@ gfx::Vector2d GLSurfaceAdapter::GetDrawOffset() const {
   return surface_->GetDrawOffset();
 }
 
+void GLSurfaceAdapter::WaitForSnapshotRendering() {
+  surface_->WaitForSnapshotRendering();
+}
+
 GLSurfaceAdapter::~GLSurfaceAdapter() {}
 
 scoped_refptr<GLSurface> InitializeGLSurfaceWithFormat(