Enforce constant size and device scale factor for surfaces

cc/surfaces/surface.cc

Index: cc/surfaces/surface.cc
diff --git a/cc/surfaces/surface.cc b/cc/surfaces/surface.cc
index 2ceae59329081c2295c5aadac3d04fb171d0742e..14846ec7c14e60e1c7dac5e500500eefc9b0d3e9 100644
--- a/cc/surfaces/surface.cc
+++ b/cc/surfaces/surface.cc
@@ -23,9 +23,9 @@ namespace cc {
 // completely damaged the first time they're drawn from.
 static const int kFrameIndexStart = 2;
 
-Surface::Surface(const SurfaceId& id, base::WeakPtr<SurfaceFactory> factory)
-    : surface_id_(id),
-      previous_frame_surface_id_(id),
+Surface::Surface(const SurfaceInfo& info, base::WeakPtr<SurfaceFactory> factory)
+    : surface_info_(info),
+      previous_frame_surface_id_(info.id()),
       factory_(factory),
       frame_index_(kFrameIndexStart),
       destroyed_(false) {}
@@ -53,6 +53,16 @@ void Surface::SetPreviousFrameSurface(Surface* surface) {
 void Surface::QueueFrame(CompositorFrame frame,
                          const DrawCallback& callback,
                          const WillDrawCallback& will_draw_callback) {
+  if (!frame.render_pass_list.empty()) {

[Fady Samuel, 2017/05/07 18:16:51]

Not necessary any more right?

[Saman Sami, 2017/05/08 20:40:32]

Done.

+    gfx::Size frame_size = frame.render_pass_list.back()->output_rect.size();
+    float device_scale_factor = frame.metadata.device_scale_factor;
+    if (frame_size != surface_info_.size_in_pixels() ||
+        device_scale_factor != surface_info_.device_scale_factor()) {

[Fady Samuel, 2017/05/01 20:36:54]

Return resources and call the callback too.

[Fady Samuel, 2017/05/07 18:16:51]

I'd love to move this test into a common place because we do it...EVERYWHERE,
and we're talking about adding more things to SurfaceInfo.

Maybe a CompositorFrame::Matches(...)? Or SurfaceInfo::Matches(...)

[Saman Sami, 2017/05/08 20:40:32]

That'll be nice, yes.

[Saman Sami, 2017/05/16 18:55:46]

Actually, I'm not sure how much that will help. I know we have the comparison
for new size vs old size all over the code base, but we rarely have a
SurfaceInfo object, perhaps because we usually keep a LocalSurfaceId as opposed
to a full SurfaceId which is necessary for SurfaceInfo.

+      DLOG(ERROR) << "Frame size doesn't match surface size.";
+      return;
+    }
+  }
+
   TakeLatencyInfoFromPendingFrame(&frame.metadata.latency_info);
 
   base::Optional<FrameData> previous_pending_frame_data =
@@ -287,7 +297,7 @@ void Surface::RunWillDrawCallback(const gfx::Rect& damage_rect) {
   if (!active_frame_data_ || active_frame_data_->will_draw_callback.is_null())
     return;
 
-  active_frame_data_->will_draw_callback.Run(surface_id_.local_surface_id(),
+  active_frame_data_->will_draw_callback.Run(surface_id().local_surface_id(),
                                              damage_rect);
 }