Re-land: cc: Fail more visibly when sync queries are not working correctly.

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 157 matching lines @@
     default:
       NOTREACHED();
       return SamplerType2D;
   }
 }
 
 // Smallest unit that impact anti-aliasing output. We use this to
 // determine when anti-aliasing is unnecessary.
 const float kAntiAliasingEpsilon = 1.0f / 1024.0f;
 
+// Block or crash if the number of pending sync queries reach this high as
+// something is seriously wrong on the service side if this happens.
+const size_t kMaxPendingSyncQueries = 16;
+
 }  // anonymous namespace
 
 class GLRenderer::ScopedUseGrContext {
  public:
   static scoped_ptr<ScopedUseGrContext> Create(GLRenderer* renderer,
                                                DrawingFrame* frame) {
     if (!renderer->output_surface_->context_provider()->GrContext())
       return scoped_ptr<ScopedUseGrContext>();
     return make_scoped_ptr(new ScopedUseGrContext(renderer, frame));
   }
@@ skipping 53 matching lines @@
 
   void End() { gl_->EndQueryEXT(GL_COMMANDS_COMPLETED_CHROMIUM); }
 
   bool IsPending() {
     unsigned available = 1;
     gl_->GetQueryObjectuivEXT(
         query_id_, GL_QUERY_RESULT_AVAILABLE_EXT, &available);
     return !available;
   }
 
+  void Wait() {
+    unsigned result = 0;
+    gl_->GetQueryObjectuivEXT(query_id_, GL_QUERY_RESULT_EXT, &result);
+  }
+
  private:
   class Fence : public ResourceProvider::Fence {
    public:
     explicit Fence(base::WeakPtr<GLRenderer::SyncQuery> query)
         : query_(query) {}
 
     // Overridden from ResourceProvider::Fence:
     virtual bool HasPassed() OVERRIDE {
       return !query_ || !query_->IsPending();
     }
@@ skipping 173 matching lines @@
 }
 
 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();
+      DCHECK(!pending_sync_queries_.front()->IsPending());
+    }
+
     while (!pending_sync_queries_.empty()) {
       if (pending_sync_queries_.front()->IsPending())
         break;
 
       available_sync_queries_.push_back(pending_sync_queries_.take_front());
     }
 
     current_sync_query_ = available_sync_queries_.empty()
                               ? make_scoped_ptr(new SyncQuery(gl_))
                               : available_sync_queries_.take_front();
@@ skipping 2767 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