[glass] Fix plots (#2943)

glass/src/lib/native/cpp/Context.cpp

@@ -15,6 +15,7 @@
 #include <imgui_internal.h>
 #include <imgui_stdlib.h>
 #include <wpi/StringRef.h>
+#include <wpi/timestamp.h>
 #include <wpigui.h>
 
 #include "glass/ContextInternal.h"
@@ -211,6 +212,10 @@ Context* glass::GetCurrentContext() { return gContext; }
 
 void glass::SetCurrentContext(Context* ctx) { gContext = ctx; }
 
+void glass::ResetTime() { gContext->zeroTime = wpi::Now(); }
+
+uint64_t glass::GetZeroTime() { return gContext->zeroTime; }
+
 Storage::Value& Storage::GetValue(wpi::StringRef key) {
   auto it = std::find(m_keys.begin(), m_keys.end(), key);
   if (it == m_keys.end()) {