Fix RegisterExternalContext() life cycle issues on WaveVR (#3691)

Fixes #3688

It turns out that WVR_RenderInit() is a blocking call that waits for the activity to be active/resumed to complete the internal work. The function is slow to react so Gecko is initializes earlier and fails all the attempts to detect VR runtimes, because the external shmem is null. We need to process InitializeJava earlier instead of waiting for the slow WVR_RenderInit to complete

app/src/wavevr/cpp/native-lib.cpp

@@ -45,6 +45,12 @@ JNI_METHOD(void, activityResumed)
 int main(int argc, char *argv[]) {
   sQueue->AttachToThread();
   VRB_LOG("Call WVR_Init");
+  sDevice = DeviceDelegateWaveVR::Create(BrowserWorld::Instance().GetRenderContext());
+  BrowserWorld::Instance().RegisterDeviceDelegate(sDevice);
+  while(!sJavaInitialized) {
+    sQueue->ProcessRunnables();
+  }
+
   WVR_InitError eError = WVR_Init(WVR_AppType_VRContent);
   if (eError != WVR_InitError_None) {
     VRB_LOG("Unable to init VR runtime: %s", WVR_GetInitErrorString(eError));
@@ -70,15 +76,10 @@ int main(int argc, char *argv[]) {
   if (pError != WVR_RenderError_None) {
     VRB_LOG("Present init failed - Error[%d]", pError);
   }
-  sDevice = DeviceDelegateWaveVR::Create(BrowserWorld::Instance().GetRenderContext());
-  BrowserWorld::Instance().RegisterDeviceDelegate(sDevice);
   VRB_GL_CHECK(glEnable(GL_DEPTH_TEST));
   VRB_GL_CHECK(glEnable(GL_CULL_FACE));
   VRB_GL_CHECK(glEnable(GL_BLEND));
   // VRB_GL_CHECK(glDisable(GL_CULL_FACE));
-  while(!sJavaInitialized) {
-    sQueue->ProcessRunnables();
-  }
   VRB_LOG("Java Initialized.");
   BrowserWorld::Instance().InitializeGL();
   BrowserWorld::Instance().Resume();