Handle new screen rotation request while waiting for the copy request callback.

ash/rotator/screen_rotation_animator.cc

Index: ash/rotator/screen_rotation_animator.cc
diff --git a/ash/rotator/screen_rotation_animator.cc b/ash/rotator/screen_rotation_animator.cc
index 9610b827db43fedb4679e7d6d674df448f9d1b1a..bc5a932c57cc6cfc224945df03c8179636d4ea9a 100644
--- a/ash/rotator/screen_rotation_animator.cc
+++ b/ash/rotator/screen_rotation_animator.cc
@@ -190,6 +190,7 @@ class ScreenRotationAnimationMetricsReporter
 ScreenRotationAnimator::ScreenRotationAnimator(int64_t display_id)
     : display_id_(display_id),
       screen_rotation_state_(IDLE),
+      rotation_request_id_(0),
       metrics_reporter_(
           base::MakeUnique<ScreenRotationAnimationMetricsReporter>()),
       disable_animation_timers_for_test_(false),
@@ -241,6 +242,13 @@ ScreenRotationAnimator::CreateAfterCopyCallback(
 void ScreenRotationAnimator::OnRootLayerCopiedBeforeRotation(
     std::unique_ptr<ScreenRotationRequest> rotation_request,
     std::unique_ptr<cc::CopyOutputResult> result) {
+  // The |rotation_request_id_| changed since last copy request, which means a
+  // new rotation stated, we need to ignore this copy result.
+  if (rotation_request->id != rotation_request_id_) {

[oshima, 2017/04/13 17:24:41]

it's probably better to have DCHECK

rotation_request->id <= rotation_reuqest_id_

[wutao, 2017/04/13 17:51:12]

Done.

+    rotation_request.reset();

[oshima, 2017/04/13 17:24:41]

it'll be reset upon return (sorry I missed others in previous review)

[wutao, 2017/04/13 17:51:12]

I removed this reset at 3 places. Please check it is correct.

+    return;
+  }
+
   // In the following cases, abort rotation:
   // 1) if the display was removed,
   // 2) the copy request has been canceled or failed. It would fail if,
@@ -378,11 +386,14 @@ void ScreenRotationAnimator::Rotate(display::Display::Rotation new_rotation,
   if (GetCurrentScreenRotation(display_id_) == new_rotation)
     return;
 
+  rotation_request_id_++;
   std::unique_ptr<ScreenRotationRequest> rotation_request =
-      base::MakeUnique<ScreenRotationRequest>(new_rotation, source);
+      base::MakeUnique<ScreenRotationRequest>(rotation_request_id_,
+                                              new_rotation, source);
 
   switch (screen_rotation_state_) {
     case IDLE:
+    case COPY_REQUESTED:
       StartRotationAnimation(std::move(rotation_request));
       break;
     case ROTATING:
@@ -392,10 +403,8 @@ void ScreenRotationAnimator::Rotate(display::Display::Rotation new_rotation,
       // |StopAnimating()|.
       StopAnimating();
       break;
-    case COPY_REQUESTED:
-      // TODO(wutao): We need to handle this otherwise the device will be in
-      // inconsistent state.
-      break;
+    default:

[oshima, 2017/04/13 17:24:41]

remove default (so that compiler can catch an error when you add new state but
forgot to update here).

[wutao, 2017/04/13 17:51:12]

Done.

+      NOTREACHED();
   }
 }
 
@@ -413,10 +422,9 @@ void ScreenRotationAnimator::ProcessAnimationQueue() {
   screen_rotation_state_ = IDLE;
   old_layer_tree_owner_.reset();
   if (last_pending_request_ && IsDisplayIdValid(display_id_)) {
-    std::unique_ptr<ScreenRotationRequest> rotation_request =
-        std::move(last_pending_request_);
-    Rotate(rotation_request->new_rotation, rotation_request->source);
-    rotation_request.reset();
+    ScreenRotationRequest rotation_request = *last_pending_request_.get();

[oshima, 2017/04/13 17:24:41]

can you just keep the new_rotation and source on stack?

[wutao, 2017/04/13 17:51:12]

Done.

+    last_pending_request_.reset();
+    Rotate(rotation_request.new_rotation, rotation_request.source);
     return;
   }