Add GPU memory usage contents browser test

content/public/common/gpu_memory_stats.h

Index: content/public/common/gpu_memory_stats.h
diff --git a/content/public/common/gpu_memory_stats.h b/content/public/common/gpu_memory_stats.h
index 5ae6e97d37884c00f846ba21c9656fb67bd8029e..e5e22f80b3fabac433be2adb71a07cde2e22a985 100644
--- a/content/public/common/gpu_memory_stats.h
+++ b/content/public/common/gpu_memory_stats.h
@@ -36,6 +36,12 @@ struct CONTENT_EXPORT GPUVideoMemoryUsageStats {
 
   // A map of processes to their GPU resource consumption
   ProcessMap process_map;
+
+  // The total amount of GPU memory allocated at the time of the request.
+  size_t bytes_allocated;
+
+  // The maximum amount of GPU memory ever allocated at once.
+  size_t bytes_allocated_historical_max;
 };
 
 }  // namespace content