blimp: Set up the CompositorDependencies for blimp in Chrome.

chrome/browser/android/blimp/chrome_compositor_dependencies.cc

+// 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 "chrome/browser/android/blimp/chrome_compositor_dependencies.h"
+
+#include "base/bind.h"
+#include "base/command_line.h"
+#include "cc/output/context_provider.h"
+#include "content/public/common/content_switches.h"
+#include "gpu/command_buffer/client/gles2_interface.h"
+#include "gpu/command_buffer/client/shared_memory_limits.h"
+#include "gpu/command_buffer/common/gles2_cmd_utils.h"
+
+namespace {
+
+bool IsValidWorkerContext(cc::ContextProvider* context_provider) {
+  if (!context_provider)

[danakj, 2016/09/01 19:26:06]

Why would it not just be a failure |result| in this case?

[Khushal, 2016/09/01 19:39:57]

Oh, I'm calling it from GetContextProviders also, where it can be null. May be I
should just do a null check there itself.

+    return false;
+
+  cc::ContextProvider::ScopedContextLock lock(context_provider);
+  return context_provider->ContextGL()->GetGraphicsResetStatusKHR() ==

[danakj, 2016/09/01 19:26:06]

Why do you check this when the context is created? It's racey at best.

[Khushal, 2016/09/01 19:39:57]

So I only do this after the worker context is bound to the current thread. Isn't
this the same that the RenderThreadImpl does?

[danakj, 2016/09/01 19:55:20]

I think it does it when checking if it should reuse it or not, not when it
creates it to see if it's valid. Maybe both of these should only be done when
checking if we should recreate or not?

[Khushal, 2016/09/01 20:10:23]

This one also checks it only during the re-use point. The second time we check
it when the compositor context is created, is that unnecessary? Also, would
become much cleaner if we remove the 2 async calls.

+         GL_NO_ERROR;
+}
+
+void OnCompositorContextCreated(
+    const blimp::client::CompositorDependencies::ContextProviderCallback&
+        callback,
+    const scoped_refptr<cc::ContextProvider>& worker_context,
+    const scoped_refptr<cc::ContextProvider>& compositor_context,
+    ui::ContextProviderFactory::ContextCreationResult result) {
+  blimp::client::CompositorDependencies::ContextProviders context_providers;
+
+  switch (result) {
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_GPU_PROCESS_INITIALIZATION_FAILED:
+      // Pass the null result to the caller and let them try again.
+      break;
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_FACTORY_SHUTDOWN:
+      // If the factory is shutting down, early out and drop the request.
+      return;
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_GPU_SURFACE_HANDLE_LOST:
+      NOTREACHED() << "We only ask for offscreen contexts";
+      break;
+    case ui::ContextProviderFactory::ContextCreationResult::SUCCESS:
+      // Return null if the worker context was invalidated while we were waiting
+      // for the compositor context.
+      if (IsValidWorkerContext(worker_context.get())) {
+        context_providers.compositor_context_provider =
+            std::move(compositor_context);
+        context_providers.worker_context_provider = std::move(worker_context);
+      }
+      break;
+  }
+
+  callback.Run(context_providers);
+}
+
+gpu::gles2::ContextCreationAttribHelper
+GetOffscreenContextCreationAttributes() {
+  gpu::gles2::ContextCreationAttribHelper attributes;
+  attributes.alpha_size = -1;
+  attributes.depth_size = 0;
+  attributes.stencil_size = 0;
+  attributes.samples = 0;
+  attributes.sample_buffers = 0;
+  attributes.bind_generates_resource = false;
+  attributes.lose_context_when_out_of_memory = true;
+  return attributes;
+}
+
+bool IsAsyncWorkerContextEnabled() {
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
+
+  if (command_line.HasSwitch(switches::kDisableGpuAsyncWorkerContext))
+    return false;
+  else if (command_line.HasSwitch(switches::kEnableGpuAsyncWorkerContext))
+    return true;
+
+  return false;
+}
+
+}  // namespace
+
+ChromeCompositorDependencies::ChromeCompositorDependencies(
+    ui::ContextProviderFactory* context_provider_factory)
+    : context_provider_factory_(context_provider_factory),
+      worker_context_request_pending_(false),
+      weak_factory_(this) {
+  DCHECK(context_provider_factory_);
+}
+
+ChromeCompositorDependencies::~ChromeCompositorDependencies() = default;
+
+gpu::GpuMemoryBufferManager*
+ChromeCompositorDependencies::GetGpuMemoryBufferManager() {
+  return context_provider_factory_->GetGpuMemoryBufferManager();
+}
+
+cc::SurfaceManager* ChromeCompositorDependencies::GetSurfaceManager() {
+  return context_provider_factory_->GetSurfaceManager();
+}
+
+uint32_t ChromeCompositorDependencies::AllocateSurfaceClientId() {
+  return context_provider_factory_->AllocateSurfaceClientId();
+}
+
+void ChromeCompositorDependencies::GetContextProviders(
+    const ContextProviderCallback& callback) {
+  if (!IsValidWorkerContext(shared_main_thread_worker_context_.get()))
+    shared_main_thread_worker_context_ = nullptr;
+
+  // Request a compositor context if the worker context is still valid.
+  if (shared_main_thread_worker_context_) {
+    HandleCompositorContextRequest(callback);
+    return;
+  }
+
+  // Add the request to the list of pending requests first, if the result
+  // comes back synchronously, the callback should get triggered.
+  pending_requests_.push_back(callback);
+
+  // If the request for a worker context is already pending, don't make
+  // another one. We'll handle all the pending requests together once the
+  // worker context is available.
+  if (worker_context_request_pending_)
+    return;
+
+  worker_context_request_pending_ = true;
+  context_provider_factory_->CreateOffscreenContextProvider(

[danakj, 2016/09/01 19:26:06]

This code here is significantly more complicated than it needs to be because
your async API here is to make the context provider instead of to get the
GpuChannelHost. If it was the latter, you'd make 1 async call and just make 2
context providers off it (see RenderThreadImpl or GpuProcessTransportFactory for
examples).

[Khushal, 2016/09/01 19:39:57]

I had to do it this way because we needed to create a
ContextProviderCommandBuffer which is a content private detail...

[danakj, 2016/09/01 19:55:20]

What if you just made a sync method to make context providers given a
GpuChannelHost returned from an async method?

[Khushal, 2016/09/01 20:10:23]

I could just hide it all in the ContextProviderFactory class, have one async
call to create the ContextProviders and internally it could use the
GpuChannelHost to create both. I think the reason I didn't do it initially was
because of the notion of shared context, sievers@ suggested that the worker
context for the browser compositors shouldn't be shared with the
BlimpCompositors. Is that something we should worry about? And even if so, may
be I can just let that class know that the contexts are for blimp so it would
cache that worker context separately?

[danakj, 2016/09/01 20:14:01]

They have LTHI on diff threads right, so no they shouldn't share. It seems like
you could make that work by saying which one you're making. Though I'd prefer
functions that return 1 thing, and just have separate functions I think. Not
entirely sure why I feel that way.. so whatever, either works, but we should
avoid 2 async calls in a row to set these up.

[Khushal, 2016/09/01 20:47:37]

So there are 3 ways I could think of doing this.

1) Ask the ContextProviderFactory for a gpu::GpuChannelHost, then provide it
back to the factory in a sync call to get the ContextProvider. This way there is
1 async call for the GpuChannelHost followed by 2 sync calls for the
ContextProviders. I'll have to add a DEPS for gpu too here then.

2) Ask the ContextProviderFactory for both the contexts in an async call and
have it cache the context internally for blimp.

3) Use 2 async calls the way we do right now.

We were hoping that the ContextProviderFactoryImpl class could hopefully be used
for aura too, there is nothing platform specific there and we can avoid
duplicacy in code. So I'll let you decide which one would looks better. :)

+      ui::ContextProviderFactory::ContextType::BLIMP_RENDER_WORKER_CONTEXT,
+      gpu::SharedMemoryLimits(), GetOffscreenContextCreationAttributes(),
+      true /* support_locking */, false /* automatic_flushes */, nullptr,
+      base::Bind(&ChromeCompositorDependencies::OnWorkerContextCreated,
+                 weak_factory_.GetWeakPtr()));
+}
+
+void ChromeCompositorDependencies::OnWorkerContextCreated(
+    const scoped_refptr<cc::ContextProvider>& worker_context,
+    ui::ContextProviderFactory::ContextCreationResult result) {
+  DCHECK(worker_context_request_pending_);
+  DCHECK(!shared_main_thread_worker_context_);
+
+  worker_context_request_pending_ = false;
+
+  switch (result) {
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_GPU_PROCESS_INITIALIZATION_FAILED:
+      // Pass the null result to the caller and let them try again.
+      break;
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_FACTORY_SHUTDOWN:
+      // If the factory is shutting down, early out and drop the requests.
+      return;
+    case ui::ContextProviderFactory::ContextCreationResult::
+        FAILURE_GPU_SURFACE_HANDLE_LOST:
+      NOTREACHED() << "We only ask for offscreen contexts";
+      break;
+    case ui::ContextProviderFactory::ContextCreationResult::SUCCESS:
+      if (worker_context->BindToCurrentThread()) {
+        shared_main_thread_worker_context_ = worker_context;
+      }
+      break;
+  }
+
+  // Copy the requests first since we can get more requests as we run these
+  // callbacks.
+  std::list<ContextProviderCallback> context_requests = pending_requests_;
+  pending_requests_.clear();
+
+  for (ContextProviderCallback& context_request : context_requests) {
+    HandleCompositorContextRequest(context_request);
+  }
+}
+
+void ChromeCompositorDependencies::HandleCompositorContextRequest(
+    const ContextProviderCallback& callback) {
+  // Respond with null contexts if the worker context could not be created.
+  if (!shared_main_thread_worker_context_) {
+    callback.Run(ContextProviders());
+    return;
+  }
+
+  ui::ContextProviderFactory::ContextProviderCallback result_callback =
+      base::Bind(&OnCompositorContextCreated, callback,
+                 shared_main_thread_worker_context_);
+
+  // The compositor context shares resources with the worker context unless
+  // the worker is async.
+  cc::ContextProvider* shared_context =
+      IsAsyncWorkerContextEnabled() ? nullptr
+                                    : shared_main_thread_worker_context_.get();
+
+  context_provider_factory_->CreateOffscreenContextProvider(
+      ui::ContextProviderFactory::ContextType::BLIMP_RENDER_COMPOSITOR_CONTEXT,
+      gpu::SharedMemoryLimits::ForMailboxContext(),
+      GetOffscreenContextCreationAttributes(), false /* support_locking */,
+      false /* automatic_flushes */, shared_context, result_callback);
+}