Re-land: cc: Make Overlay unit tests work when sync query extension is available.

cc/output/gl_renderer.cc

 // Copyright 2010 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/output/gl_renderer.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <string>
@@ skipping 448 matching lines @@
 }
 
 static ResourceProvider::ResourceId WaitOnResourceSyncPoints(
     ResourceProvider* resource_provider,
     ResourceProvider::ResourceId resource_id) {
   resource_provider->WaitSyncPointIfNeeded(resource_id);
   return resource_id;
 }
 
 void GLRenderer::BeginDrawingFrame(DrawingFrame* frame) {
-  if (frame->device_viewport_rect.IsEmpty())
-    return;
-
   TRACE_EVENT0("cc", "GLRenderer::BeginDrawingFrame");
 
   scoped_refptr<ResourceProvider::Fence> read_lock_fence;
   if (use_sync_query_) {
     // Block until oldest sync query has passed if the number of pending queries
     // ever reach kMaxPendingSyncQueries.
     if (pending_sync_queries_.size() >= kMaxPendingSyncQueries) {
       LOG(ERROR) << "Reached limit of pending sync queries.";
 
       pending_sync_queries_.front()->Wait();
@@ skipping 10 matching lines @@
     current_sync_query_ = available_sync_queries_.empty()
                               ? make_scoped_ptr(new SyncQuery(gl_))
                               : available_sync_queries_.take_front();
 
     read_lock_fence = current_sync_query_->Begin();
   } else {
     read_lock_fence = make_scoped_refptr(new FallbackFence(gl_));
   }
   resource_provider_->SetReadLockFence(read_lock_fence.get());
 
+  if (frame->device_viewport_rect.IsEmpty())

[danakj, 2014/10/29 15:18:26]

If there's an empty viewport can you not just make FinishDrawingFrame early out
and not do a bunch of work here?

[reveman, 2014/10/29 16:14:52]

Maybe. It would assume that we're not performing any operations that require a
read lock fence in these cases. It's not clear from this code if that is safe.

Alternatively, we could just remove this check and leave it up to the caller.

[danakj, 2014/10/29 17:04:38]

ie make DirectRenderer check this? That sounds good.

+    return;
+
   // Insert WaitSyncPointCHROMIUM on quad resources prior to drawing the frame,
   // so that drawing can proceed without GL context switching interruptions.
   DrawQuad::ResourceIteratorCallback wait_on_resource_syncpoints_callback =
       base::Bind(&WaitOnResourceSyncPoints, resource_provider_);
 
   for (size_t i = 0; i < frame->render_passes_in_draw_order->size(); ++i) {
     RenderPass* pass = frame->render_passes_in_draw_order->at(i);
     for (auto& quad : pass->quad_list)
       quad.IterateResources(wait_on_resource_syncpoints_callback);
   }
@@ skipping 2849 matching lines @@
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order,
         overlay.transform,
         pending_overlay_resources_.back()->texture_id(),
         overlay.display_rect,
         overlay.uv_rect);
   }
 }
 
 }  // namespace cc