content: Add ContextProviderFactory to create a render ContextProvider.

ui/android/context_provider_factory.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.
+
+#ifndef UI_ANDROID_CONTEXT_PROVIDER_FACTORY_H_
+#define UI_ANDROID_CONTEXT_PROVIDER_FACTORY_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "ui/android/ui_android_export.h"
+
+namespace cc {
+class ContextProvider;
+class VulkanContextProvider;
+}
+
+namespace ui {
+
+// This class is not thread-safe and should only be accessed from the UI thread.
+class UI_ANDROID_EXPORT ContextProviderFactory {

[danakj, 2016/07/29 01:26:15]

Hm, I'm planning to make a ContextProvider::Factory..

https://codereview.chromium.org/1985973002/diff/80001/cc/output/context_provi...

That defers creation to another thread. Why are you not using the contexts on
RenderThreadImpl?

[Khushal, 2016/07/29 02:07:36]

Your change looks like it is to have cc embedder pass in a factory so we can ask
them to create the context on the compositor thread.

This ContextProviderFactory is so blimp can ask content to create a context
provider, since it requires access to GpuChannelHost and CommandBuffer, which
are in content and we can't use any of the content code in blimp. After your
change, this class will create a ContextProvider::Factory I guess.

It would be nice to move the setup for the render contexts so we can at least
share it with the impl of this class. Perhaps moving it to someplace in
content/common because the impl of this class will live in the browser.

+ public:
+  struct ContextProviders {
+    ContextProviders();
+    ~ContextProviders();
+
+    scoped_refptr<cc::VulkanContextProvider> vulkan_context_provider;
+
+    scoped_refptr<cc::ContextProvider> compositor_context_provider;
+    scoped_refptr<cc::ContextProvider> worker_context_provider;
+  };
+
+  using ContextProviderCallback = base::Callback<void(const ContextProviders&)>;
+
+  static ContextProviderFactory* GetInstance();
+
+  // This should only be called once, on startup. Ownership remains with the
+  // caller.
+  static void SetInstance(ContextProviderFactory* context_provider_factory);
+
+  virtual ~ContextProviderFactory(){};
+
+  // Creates a ContextProvider with an offscreen context for a compositor
+  // rendering web content.
+  virtual void RequestRenderContextProvider(
+      ContextProviderCallback result_callback) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_ANDROID_CONTEXT_PROVIDER_FACTORY_H_