Free worker context resources on idle.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index be2f9b1376bf5c2994b23b544c0bbdf9f6e7081f..5843061c42a23eaa8fb7c1b02de6b653f0278c92 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -123,6 +123,7 @@
 #include "content/renderer/shared_worker/embedded_shared_worker_stub.h"
 #include "gin/public/debug.h"
 #include "gpu/GLES2/gl2extchromium.h"
+#include "gpu/command_buffer/client/context_support.h"
 #include "gpu/command_buffer/client/shared_memory_limits.h"
 #include "gpu/ipc/client/command_buffer_proxy_impl.h"
 #include "gpu/ipc/client/gpu_channel_host.h"
@@ -160,6 +161,7 @@
 #include "third_party/WebKit/public/web/WebView.h"
 #include "third_party/icu/source/i18n/unicode/timezone.h"
 #include "third_party/skia/include/core/SkGraphics.h"
+#include "third_party/skia/include/gpu/GrContext.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_base_switches.h"
 
@@ -440,6 +442,24 @@ bool IsRunningInMash() {
   return cmdline->HasSwitch(switches::kIsRunningInMash);
 }
 
+void OnSharedWorkerContextIdle(cc::ContextProvider* context_provider) {
+  // If we can't acquire the lock, someone has started using this context, so
+  // we are no longer idle.
+  base::Lock* lock = context_provider->GetLock();
+  if (!lock->Try())
+    return;
+
+  context_provider->DetachFromThread();
+  context_provider->BindToCurrentThread();
+
+  context_provider->DeleteCachedResources();
+  context_provider->ContextSupport()->TrimResources();

[danakj, 2016/08/23 01:26:24]

Why do we need a separate TrimResources from DeleteCachedResources?

+
+  // Detach from thread to allow a new thread to attach.
+  context_provider->DetachFromThread();
+  lock->Release();
+}
+
 }  // namespace
 
 // For measuring memory usage after each task. Behind a command line flag.
@@ -2126,6 +2146,14 @@ RenderThreadImpl::SharedCompositorWorkerContextProvider() {
       stream_priority);
   if (!shared_worker_context_provider_->BindToCurrentThread())
     shared_worker_context_provider_ = nullptr;
+
+  // Set the idle callback. This callback is only called if ContextSupport
+  // is alive, so we know that the unreatained worker context provider

[danakj, 2016/08/23 01:26:24]

unretained

+  // pointer will also be alive.
+  shared_worker_context_provider_->ContextSupport()->SetIdleCallback(
+      base::Bind(&OnSharedWorkerContextIdle,
+                 base::Unretained(shared_worker_context_provider_.get())),
+      base::ThreadTaskRunnerHandle::Get());

[danakj, 2016/08/23 01:26:24]

what about just making it use the task runner the context is bound to? thats how
the callbacks on ContextProvider work

[ericrk, 2016/08/24 18:32:21]

The current callback systems always funnels through the Context/GpuControl.
Depending on the implementation, the Context/GpuControl may not have a task
runner (and may run callbacks directly), although typically it does have one.

It seems like we could:
- expose the task runner on GpuControl, and allow it to return null.
- Add a "ScheduleTask" and "ScheduleDelayedTask" to GpuControl, but at that
point we might as well just return the task runner?
- Move the idle callback to GpuControl/Context, although this would require some
new logic in each implementation of GpuControl/Context (similar to our other
callbacks I guess?)

   return shared_worker_context_provider_;
 }