Allow canvases to be GPU-accelerated in Workers

third_party/WebKit/Source/platform/graphics/gpu/SharedGpuContext.h

+// Copyright 2016 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.
+
+#include "wtf/ThreadSpecific.h"
+
+#include <memory>
+
+namespace gpu { namespace gles2 { class GLES2Interface; } }
+class GrContext;
+
+namespace blink {
+
+class WaitableEvent;
+class WebGraphicsContext3DProvider;
+
+// SharedGpuContext provides access to a thread-specific GPU context
+// that is shared by many callsites throughout the thread.
+// When on the main thread, provides access to the same context as
+// Platform::createSharedOffscreenGraphicsContext3DProvider
+class SharedGpuContext {
+public:
+    // The contextId is incremented each time a new underlying context
+    // is created. For example, when the context is lost, then restored.
+    // User code can rely on this Id to determine whether long-lived
+    // gpu resources are still alive in the current context.
+    static unsigned contextId();
+    static gpu::gles2::GLES2Interface* gl();
+    static GrContext* gr();
+    static bool isValid();
+    static bool restore();
+
+    enum {
+        kNoSharedContext = 0,
+    };
+
+private:
+    static SharedGpuContext* getInstanceForCurrentThread();
+
+    SharedGpuContext();
+    void createContextProviderOnMainThread(WaitableEvent*);
+    void createContextProvider();
+
+    std::unique_ptr<WebGraphicsContext3DProvider> m_contextProvider;
+    unsigned m_contextId;
+    friend class WTF::ThreadSpecific<SharedGpuContext>;
+};
+
+} // blink