gpu: Add callback for yielding command buffer execution.

gpu/command_buffer/service/command_executor.h

 // Copyright (c) 2012 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 GPU_COMMAND_BUFFER_SERVICE_COMMAND_EXECUTOR_H_
 #define GPU_COMMAND_BUFFER_SERVICE_COMMAND_EXECUTOR_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <queue>
 
-#include "base/atomic_ref_count.h"
-#include "base/atomicops.h"
 #include "base/callback.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "gpu/command_buffer/service/cmd_buffer_engine.h"
 #include "gpu/command_buffer/service/cmd_parser.h"
 #include "gpu/command_buffer/service/command_buffer_service.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 #include "gpu/gpu_export.h"
 
 namespace gpu {
 
-class PreemptionFlag : public base::RefCountedThreadSafe<PreemptionFlag> {
- public:
-  PreemptionFlag() : flag_(0) {}
-
-  bool IsSet() { return !base::AtomicRefCountIsZero(&flag_); }
-  void Set() { base::AtomicRefCountInc(&flag_); }
-  void Reset() { base::subtle::NoBarrier_Store(&flag_, 0); }
-
- private:
-  base::AtomicRefCount flag_;
-
-  ~PreemptionFlag() {}
-
-  friend class base::RefCountedThreadSafe<PreemptionFlag>;
-};
-
 // This class schedules commands that have been flushed. They are received via
 // a command buffer and forwarded to a command parser. TODO(apatrick): This
 // class should not know about the decoder. Do not add additional dependencies
 // on it.
 class GPU_EXPORT CommandExecutor
     : NON_EXPORTED_BASE(public CommandBufferEngine),
       public base::SupportsWeakPtr<CommandExecutor> {
  public:
   CommandExecutor(CommandBufferServiceBase* command_buffer,
                   AsyncAPIInterface* handler,
                   gles2::GLES2Decoder* decoder);
 
   ~CommandExecutor() override;
 
   void PutChanged();
 
-  void SetPreemptByFlag(scoped_refptr<PreemptionFlag> flag) {
-    preemption_flag_ = flag;
-  }
-
   // Sets whether commands should be processed by this scheduler. Setting to
   // false unschedules. Setting to true reschedules.
   void SetScheduled(bool scheduled);
 
   bool scheduled() const { return scheduled_; }
 
   // Returns whether the scheduler needs to be polled again in the future to
   // process pending queries.
   bool HasPendingQueries() const;
 
   // Process pending queries and return. HasPendingQueries() can be used to
   // determine if there's more pending queries after this has been called.
   void ProcessPendingQueries();
 
   // Implementation of CommandBufferEngine.
   scoped_refptr<Buffer> GetSharedMemoryBuffer(int32_t shm_id) override;
   void set_token(int32_t token) override;
   bool SetGetBuffer(int32_t transfer_buffer_id) override;
   bool SetGetOffset(int32_t offset) override;
   int32_t GetGetOffset() override;
 
   void SetCommandProcessedCallback(const base::Closure& callback);
 
+  using PauseExecutionCallback = base::Callback<bool(void)>;
+  void SetPauseExecutionCallback(const PauseExecutionCallback& callback);
+
   // Returns whether the scheduler needs to be polled again in the future to
   // process idle work.
   bool HasMoreIdleWork() const;
 
   // Perform some idle work and return. HasMoreIdleWork() can be used to
   // determine if there's more idle work do be done after this has been called.
   void PerformIdleWork();
 
   // Whether there is state that needs to be regularly polled.
   bool HasPollingWork() const;
   void PerformPollingWork();
 
   CommandParser* parser() const { return parser_.get(); }
 
  private:
-  bool IsPreempted();
+  bool PauseExecution();
 
   // The CommandExecutor holds a weak reference to the CommandBuffer. The
   // CommandBuffer owns the CommandExecutor and holds a strong reference to it
   // through the ProcessCommands callback.
   CommandBufferServiceBase* command_buffer_;
 
   // The parser uses this to execute commands.
   AsyncAPIInterface* handler_;
 
   // Does not own decoder. TODO(apatrick): The CommandExecutor shouldn't need a
   // pointer to the decoder, it is only used to initialize the CommandParser,
   // which could be an argument to the constructor, and to determine the
   // reason for context lost.
   gles2::GLES2Decoder* decoder_;
 
   // TODO(apatrick): The CommandExecutor currently creates and owns the parser.
   // This should be an argument to the constructor.
   std::unique_ptr<CommandParser> parser_;
 
   // Whether the scheduler is currently able to process more commands.
-  bool scheduled_;
+  bool scheduled_ = true;
 
   base::Closure command_processed_callback_;
 
-  // If non-NULL and |preemption_flag_->IsSet()|, exit PutChanged early.
-  scoped_refptr<PreemptionFlag> preemption_flag_;
-  bool was_preempted_;
+  // If this callback returns true, exit PutChanged early.
+  PauseExecutionCallback pause_execution_callback_;
+  bool paused_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(CommandExecutor);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_COMMAND_EXECUTOR_H_