cc: Fix infinite BeginFrame that Scheduler causes.

cc/scheduler/scheduler.cc

 // Copyright 2011 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 "cc/scheduler/scheduler.h"
 
 #include "base/auto_reset.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 
@@ skipping 128 matching lines @@
       settings_.using_synchronous_renderer_compositor;
 
   if (needs_begin_frame_to_draw)
     safe_to_expect_begin_frame_ = true;
 
   // Determine if we need BeginFrame notifications.
   // If we do, always request the BeginFrame immediately.
   // If not, only disable on the next BeginFrame to avoid unnecessary toggles.
   // The synchronous renderer compositor requires immediate disables though.
   if ((needs_begin_frame ||
        state_machine_.inside_begin_frame() ||

[brianderson, 2013/06/24 18:04:49]

The intent of state_machine_.inside_begin_frame(), in this if statement was to
avoid disabling SetNeedsBeginFrame until the next BeginFrame, in case it was
re-enabled before the next BeginFrame.

Otherwise, there could be a disable glitch that gets picked up by the BeginFrame
provider causing us to lose a BeginFrame.

Apparently, it is not being disabled on the next BeginFrame though. Do you
happen to know why? I'm still trying to figure it out myself.

        immediate_disables_needed) &&
       (needs_begin_frame != last_set_needs_begin_frame_)) {
     has_pending_begin_frame_ = false;
     client_->SetNeedsBeginFrameOnImplThread(needs_begin_frame);
     if (safe_to_expect_begin_frame_)
       last_set_needs_begin_frame_ = needs_begin_frame;
   }
 
   // Request another BeginFrame if we haven't drawn for now until we have
   // deadlines implemented.
   if (state_machine_.inside_begin_frame() && has_pending_begin_frame_) {
     has_pending_begin_frame_ = false;
     client_->SetNeedsBeginFrameOnImplThread(true);
     return;
   }
+
+  client_->SetNeedsBeginFrameOnImplThread(needs_begin_frame_to_draw);

[brianderson, 2013/06/24 18:04:49]

We should avoid disabling SetNeedsBeginFrame until the next BeginFrame, so we
can't put this here.

+  if (safe_to_expect_begin_frame_)
+    last_set_needs_begin_frame_ = needs_begin_frame_to_draw;
 }
 
 void Scheduler::BeginFrame(const BeginFrameArgs& args) {
   TRACE_EVENT0("cc", "Scheduler::BeginFrame");
   DCHECK(!has_pending_begin_frame_);
   has_pending_begin_frame_ = true;
   safe_to_expect_begin_frame_ = true;
   last_begin_frame_args_ = args;
   state_machine_.DidEnterBeginFrame(args);
   ProcessScheduledActions();
@@ skipping 59 matching lines @@
 
   SetupNextBeginFrameIfNeeded();
   client_->DidAnticipatedDrawTimeChange(AnticipatedDrawTime());
 }
 
 bool Scheduler::WillDrawIfNeeded() const {
   return !state_machine_.DrawSuspendedUntilCommit();
 }
 
 }  // namespace cc