content: Add ContextProviderFactory to create a render ContextProvider.

content/browser/renderer_host/context_provider_factory_impl_android.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 CONTENT_BROWSER_RENDERER_HOST_CONTEXT_PROVIDER_FACTORY_IMPL_ANDROID_H_
+#define CONTENT_BROWSER_RENDERER_HOST_CONTEXT_PROVIDER_FACTORY_IMPL_ANDROID_H_
+
+#include <list>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/timer/timer.h"
+#include "content/common/content_export.h"
+#include "ui/android/context_provider_factory.h"
+
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
+namespace cc {
+class VulkanInProcessContextProvider;
+}
+
+namespace gpu {
+class GpuChannelHost;
+}
+
+namespace content {
+class ContextProviderCommandBuffer;
+
+class CONTENT_EXPORT ContextProviderFactoryImpl
+    : public ui::ContextProviderFactory {
+ public:
+  using GpuChannelRequestCallback =
+      base::Callback<void(scoped_refptr<gpu::GpuChannelHost>)>;
+
+  static ContextProviderFactoryImpl* GetInstance();
+
+  ~ContextProviderFactoryImpl() override;
+
+  // ContextProviderFactory implementation.
+  void RequestRenderContextProvider(
+      ContextProviderCallback result_callback) override;
+  cc::SurfaceManager* GetSurfaceManager() override;
+  uint32_t AllocateSurfaceClientId() override;
+
+  void RequestGpuChannel(

[no sievers, 2016/07/29 19:14:31]

Could we maybe make this 'private' by also having the actual context creation go
through here for the browser compositor?

Basically instead of CompositorImpl::CreateOutputSurface(gpu_channel_host) make
it CompositorImpl::CreateOutputSurface(context_provider).

You might have to pass in a few things like the SharedMemoryLimits (and surface
id for onscreen), but then also see the comment below which that would probably
address.

[no sievers, 2016/07/29 19:42:51]

Ok I see now what the slightly tricky part if with the onscreen context:

If surfaceDestroyed() happens while we are establishing a GPU channel, then we
must not try to create an OutputSurface with that surface_id. It's the early-out
here:

void CompositorImpl::CreateOutputSurface() {
  // We might have had a request from a LayerTreeHost that was then
  // hidden (and hidden means we don't have a native surface).
  // Also make sure we only handle this once.
  if (!output_surface_request_pending_ || !host_->visible())
    return;

Maybe it's good enough though to check with the GpuSurfaceTracker or so to see
if it's still valid before we attempt to create an onscreen context with it.

+      GpuChannelRequestCallback gpu_channel_request_callback);
+
+  scoped_refptr<cc::VulkanInProcessContextProvider>
+  GetSharedVulkanContextProviderAndroid();
+
+ private:
+  friend struct base::DefaultSingletonTraits<ContextProviderFactoryImpl>;
+
+  ContextProviderFactoryImpl();
+
+  // Will return nullptr if the Gpu channel has not been established.
+  gpu::GpuChannelHost* EnsureGpuChannelEstablished();
+  void OnGpuChannelEstablished();
+  void OnGpuChannelTimeout();
+
+  void HandlePendingRequests();
+
+  void CreateRenderCompositorContexts(

[no sievers, 2016/07/29 19:14:30]

Something is a bit funky about this:

This implementation lives in content/browser/renderer_host, so it shouldn't deal
with 'renderer' stuff.
And also the browser compositor does not use the context factory in here at all.

[Khushal, 2016/07/29 21:30:55]

Render is a bad word. I called it that because effectively the Blimp compositor
will do the work that the renderer compositor does.
Will move that to this class within this patch too.

+      ContextProviders& context_providers,
+      scoped_refptr<gpu::GpuChannelHost> gpu_channel_host);
+
+  scoped_refptr<ContextProviderCommandBuffer>
+  SharedCompositorWorkerContextProvider(
+      scoped_refptr<gpu::GpuChannelHost> gpu_channel_host);
+
+  GpuChannelRequestCallback gpu_channel_request_callback_;
+  std::list<ContextProviderCallback> render_context_request_callbacks_;
+
+  scoped_refptr<ContextProviderCommandBuffer> shared_worker_context_provider_;
+
+  bool in_handle_pending_requests_;
+
+  base::OneShotTimer establish_gpu_channel_timeout_;
+
+  std::unique_ptr<cc::SurfaceManager> surface_manager_;
+  int surface_client_id_;
+
+  base::WeakPtrFactory<ContextProviderFactoryImpl> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContextProviderFactoryImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_CONTEXT_PROVIDER_FACTORY_IMPL_ANDROID_H_