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diff --git a/gfx/layers/ProfilerScreenshots.h b/gfx/layers/ProfilerScreenshots.h
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+++ b/gfx/layers/ProfilerScreenshots.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_ProfilerScreenshots_h
+#define mozilla_layers_ProfilerScreenshots_h
+
+#include <functional>
+
+#include "mozilla/Mutex.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/TimeStamp.h"
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+
+#include "mozilla/gfx/Point.h"
+
+class nsIThread;
+
+namespace mozilla {
+
+namespace gfx {
+class DataSourceSurface;
+}
+
+namespace layers {
+
+/**
+ * Can be used to submit screenshots from the compositor to the profiler.
+ * Screenshots have a fixed bounding size. The user of this class will usually
+ * scale down the window contents first, ideally on the GPU, then read back the
+ * small scaled down image into main memory, and then call SubmitScreenshot to
+ * pass the data to the profiler.
+ * This class encodes each screenshot to a JPEG data URL, on a separate thread.
+ * This class manages that thread and recycles memory buffers.
+ */
+class ProfilerScreenshots final {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ProfilerScreenshots)
+
+ public:
+  ProfilerScreenshots();
+
+  /**
+   * Returns whether the profiler is currently active and is running with the
+   * "screenshots" feature enabled.
+   */
+  static bool IsEnabled();
+
+  /**
+   * Returns a fixed size that all screenshots should be resized to fit into.
+   */
+  static gfx::IntSize ScreenshotSize() { return gfx::IntSize(350, 350); }
+
+  /**
+   * The main functionality provided by this class.
+   * This method will synchronously invoke the supplied aPopulateSurface
+   * callback function with a DataSourceSurface in which the callback should
+   * store the pixel data. This surface may be larger than aScaledSize, but
+   * only the data in the rectangle (0, 0, aScaledSize.width,
+   * aScaledSize.height) will be read.
+   * @param aWindowIdentifier A pointer-sized integer that can be used to match
+   *   up multiple screenshots from the same window.
+   * @param aOriginalSize The unscaled size of the snapshotted window.
+   * @param aScaledSize The scaled size, aScaled <= ScreenshotSize(), which the
+   *   snapshot has been resized to.
+   * @param aTimeStamp The time at which the snapshot was taken. In
+   *   asynchronous readback implementations, this is the time at which the
+   *   readback / copy command was put into the command stream to the GPU, not
+   *   the time at which the readback data was mapped into main memory.
+   * @param aPopulateSurface A callback that the caller needs to implement,
+   *   which needs to copy the screenshot pixel data into the surface that's
+   *   supplied to the callback. Called zero or one times, synchronously.
+   */
+  void SubmitScreenshot(
+      uintptr_t aWindowIdentifier, const gfx::IntSize& aOriginalSize,
+      const gfx::IntSize& aScaledSize, const TimeStamp& aTimeStamp,
+      const std::function<bool(gfx::DataSourceSurface*)>& aPopulateSurface);
+
+ private:
+  ~ProfilerScreenshots();
+
+  /**
+   * Recycle a surface from mAvailableSurfaces or create a new one if all
+   * surfaces are currently in use, up to some maximum limit.
+   * Returns null if the limit is reached.
+   * Can be called on any thread.
+   */
+  already_AddRefed<gfx::DataSourceSurface> TakeNextSurface();
+
+  /**
+   * Return aSurface back into the mAvailableSurfaces pool. Can be called on
+   * any thread.
+   */
+  void ReturnSurface(gfx::DataSourceSurface* aSurface);
+
+  // An array of surfaces ready to be recycled. Can be accessed from multiple
+  // threads, protected by mMutex.
+  nsTArray<RefPtr<gfx::DataSourceSurface>> mAvailableSurfaces;
+  // Protects mAvailableSurfaces.
+  Mutex mMutex;
+  // The total number of surfaces created. If encoding is fast enough to happen
+  // entirely in the time between two calls to SubmitScreenshot, this should
+  // never exceed 1.
+  uint32_t mLiveSurfaceCount;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_ProfilerScreenshots_h