[cc] Adds source_id and sequence_number to BeginFrameArgs.

cc/scheduler/begin_frame_source.h

 // Copyright 2014 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 CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 #define CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <set>
 #include <string>
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/scheduler/delay_based_time_source.h"
 
 namespace cc {
 
 // (Pure) Interface for observing BeginFrame messages from BeginFrameSource
 // objects.
 class CC_EXPORT BeginFrameObserver {
  public:
   virtual ~BeginFrameObserver() {}
 
   // The |args| given to OnBeginFrame is guaranteed to have
-  // |args|.IsValid()==true and have |args|.frame_time
-  // field be strictly greater than the previous call.
+  // |args|.IsValid()==true. If |args|.source_id did not change between
+  // invocations, |args|.sequence_number is guaranteed to be be strictly greater
+  // than the previous call. Further, |args|.frame_time is guaranteed to be
+  // greater than or equal to the previous call even if the source_id changes.
   //
   // Side effects: This function can (and most of the time *will*) change the
   // return value of the LastUsedBeginFrameArgs method. See the documentation
   // on that method for more information.
   virtual void OnBeginFrame(const BeginFrameArgs& args) = 0;
 
   // Returns the last BeginFrameArgs used by the observer. This method's return
   // value is affected by the OnBeginFrame method!
   //
   //  - Before the first call of OnBeginFrame, this method should return a
@@ skipping 51 matching lines @@
 // BeginFrameObserver.
 //
 // BeginFrame calls *normally* occur just after a vsync interrupt when input
 // processing has been finished and provide information about the time values
 // of the vsync times. *However*, these values can be heavily modified or even
 // plain made up (when no vsync signal is available or vsync throttling is
 // turned off). See the BeginFrameObserver for information about the guarantees
 // all BeginFrameSources *must* provide.
 class CC_EXPORT BeginFrameSource {
  public:
+  BeginFrameSource();
   virtual ~BeginFrameSource() {}
 
   // DidFinishFrame provides back pressure to a frame source about frame
   // processing (rather than toggling SetNeedsBeginFrames every frame). It is
   // used by systems like the BackToBackFrameSource to make sure only one frame
   // is pending at a time.
   virtual void DidFinishFrame(BeginFrameObserver* obs,
                               size_t remaining_frames) = 0;
 
   // Add/Remove an observer from the source. When no observers are added the BFS
   // should shut down its timers, disable vsync, etc.
   virtual void AddObserver(BeginFrameObserver* obs) = 0;
   virtual void RemoveObserver(BeginFrameObserver* obs) = 0;
 
   // Returns false if the begin frame source will just continue to produce
   // begin frames without waiting.
   virtual bool IsThrottled() const = 0;
+
+  // Returns an identifier for this BeginFrameSource. Guaranteed unique within a
+  // process, but not across processes. This is used to create BeginFrames that
+  // originate at this source. Note that BeginFrameSources may pass on
+  // BeginFrames created by other sources, with different IDs.
+  uint32_t source_id() const;
+
+ private:
+  uint32_t source_id_;
 };
 
 // A BeginFrameSource that does nothing.
 class CC_EXPORT StubBeginFrameSource : public BeginFrameSource {
  public:
   void DidFinishFrame(BeginFrameObserver* obs,
                       size_t remaining_frames) override {}
   void AddObserver(BeginFrameObserver* obs) override {}
   void RemoveObserver(BeginFrameObserver* obs) override {}
   bool IsThrottled() const override;
@@ skipping 31 matching lines @@
                                base::TimeDelta interval) override {}
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override {}
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
  private:
   std::unique_ptr<DelayBasedTimeSource> time_source_;
   std::unordered_set<BeginFrameObserver*> observers_;
   std::unordered_set<BeginFrameObserver*> pending_begin_frame_observers_;
+  uint64_t next_sequence_number_;
   base::WeakPtrFactory<BackToBackBeginFrameSource> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BackToBackBeginFrameSource);
 };
 
 // A frame source which is locked to an external parameters provides from a
 // vsync source and generates BeginFrameArgs for it.
 class CC_EXPORT DelayBasedBeginFrameSource : public SyntheticBeginFrameSource,
                                              public DelayBasedTimeSourceClient {
  public:
@@ skipping 10 matching lines @@
 
   // SyntheticBeginFrameSource implementation.
   void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                base::TimeDelta interval) override;
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override;
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
  private:
-  BeginFrameArgs CreateBeginFrameArgs(base::TimeTicks frame_time,
+  BeginFrameArgs CreateBeginFrameArgs(uint64_t sequence_number,
+                                      base::TimeTicks frame_time,
                                       BeginFrameArgs::BeginFrameArgsType type);
 
   std::unique_ptr<DelayBasedTimeSource> time_source_;
   std::unordered_set<BeginFrameObserver*> observers_;
   base::TimeTicks last_timebase_;
   base::TimeDelta authoritative_interval_;
+  BeginFrameArgs current_begin_frame_args_;
 
   DISALLOW_COPY_AND_ASSIGN(DelayBasedBeginFrameSource);
 };
 
 class CC_EXPORT ExternalBeginFrameSourceClient {
  public:
   // Only called when changed.  Assumed false by default.
   virtual void OnNeedsBeginFrames(bool needs_begin_frames) = 0;
 };
 
@@ skipping 23 matching lines @@
   ExternalBeginFrameSourceClient* client_;
   bool paused_ = false;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ExternalBeginFrameSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_