gpu: Fix some context lost marking glitches+leaks and add UMA stats

content/common/gpu/client/command_buffer_metrics.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_METRICS_H_
+#define CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_METRICS_H_
+
+#include <string>
+
+#include "gpu/command_buffer/common/constants.h"
+
+namespace content {
+
+enum CommandBufferContextType {
+  // Don't add new values before _MAX_ENUM to keep the histogram consistent.

[Ken Russell (switch to Gerrit), 2015/04/24 02:39:41]

Is this comment correct? Should it read "before" or "after"?

+  BROWSER_COMPOSITOR_ONSCREEN_CONTEXT,
+  BROWSER_OFFSCREEN_MAINTHREAD_CONTEXT,
+  RENDER_COMPOSITOR_CONTEXT,
+  RENDER_WORKER_CONTEXT,
+  RENDERER_MAINTHREAD_CONTEXT,
+  GPU_VIDEO_ACCELERATOR_CONTEXT,
+  OFFSCREEN_VIDEO_CAPTURE_CONTEXT,
+  OFFSCREEN_CONTEXT_FOR_WEBGL,
+  CONTEXT_TYPE_UNKNOWN,
+  OFFSCREEN_CONTEXT_FOR_TESTING = CONTEXT_TYPE_UNKNOWN,
+  // Add new values above this point.

[Ken Russell (switch to Gerrit), 2015/04/24 02:39:41]

Above this point or above CONTEXT_TYPE_UNKNOWN?

[no sievers, 2015/04/24 18:52:47]

Done.

+  CONTEXT_TYPE_MAX_ENUM = CONTEXT_TYPE_UNKNOWN
+  // not reported
+};
+
+std::string CommandBufferContextTypeToString(CommandBufferContextType type);
+
+void UmaRecordContextInitFailed(CommandBufferContextType type);
+
+void UmaRecordContextLost(CommandBufferContextType type,
+                          gpu::error::Error error,
+                          gpu::error::ContextLostReason reason);
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_CLIENT_COMMAND_BUFFER_METRICS_H_