Reuse GLFenceNV when an existing CommandsCompletedQuery is reused

ui/gl/gl_fence_nv.cc

 // Copyright 2014 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 "ui/gl/gl_fence_nv.h"
 
 #include "ui/gl/gl_bindings.h"
 
 namespace gfx {
 
 GLFenceNV::GLFenceNV() {
   // What if either of these GL calls fails? TestFenceNV will return true.
   // See spec:
   // http://www.opengl.org/registry/specs/NV/fence.txt
   //
   // What should happen if TestFenceNV is called for a name before SetFenceNV
   // is called?
   //     We generate an INVALID_OPERATION error, and return TRUE.
   //     This follows the semantics for texture object names before
   //     they are bound, in that they acquire their state upon binding.
   //     We will arbitrarily return TRUE for consistency.
   glGenFencesNV(1, &fence_);
+  ResetState();
+}
+
+bool GLFenceNV::ResetSupported() {
+  return true;
+}
+
+void GLFenceNV::ResetState() {
   glSetFenceNV(fence_, GL_ALL_COMPLETED_NV);
   DCHECK(glIsFenceNV(fence_));
   glFlush();
 }
 
 bool GLFenceNV::HasCompleted() {
   DCHECK(glIsFenceNV(fence_));
   return !!glTestFenceNV(fence_);
 }
 
 void GLFenceNV::ClientWait() {
   DCHECK(glIsFenceNV(fence_));
   glFinishFenceNV(fence_);
 }
 
 void GLFenceNV::ServerWait() {
   DCHECK(glIsFenceNV(fence_));
   ClientWait();
 }
 
 GLFenceNV::~GLFenceNV() {
   DCHECK(glIsFenceNV(fence_));
   glDeleteFencesNV(1, &fence_);
 }
 
 }  // namespace gfx