gpu: Bind dummy GL API when no context is current

ui/gl/gl_context.cc

 // Copyright (c) 2012 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 <string>
 
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/threading/thread_local.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_gl_api_implementation.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface.h"
 #include "ui/gl/gl_switches.h"
 #include "ui/gl/gl_version_info.h"
 
 namespace gfx {
 
 namespace {
 base::LazyInstance<base::ThreadLocalPointer<GLContext> >::Leaky
     current_context_ = LAZY_INSTANCE_INITIALIZER;
 
 base::LazyInstance<base::ThreadLocalPointer<GLContext> >::Leaky
     current_real_context_ = LAZY_INSTANCE_INITIALIZER;
 }  // namespace
 
+GLContext::ScopedReleaseCurrent::ScopedReleaseCurrent() : canceled_(false) {}
+
+GLContext::ScopedReleaseCurrent::~ScopedReleaseCurrent() {
+  if (!canceled_ && GetCurrent()) {
+    GetCurrent()->ReleaseCurrent(NULL);
+  }
+}
+
+void GLContext::ScopedReleaseCurrent::Cancel() {
+  canceled_ = true;
+}
+
 GLContext::GLContext(GLShareGroup* share_group) : share_group_(share_group) {
   if (!share_group_.get())
     share_group_ = new GLShareGroup;
 
   share_group_->AddContext(this);
 }
 
 GLContext::~GLContext() {
   share_group_->RemoveContext(this);
   if (GetCurrent() == this) {
@@ skipping 79 matching lines @@
   return current_context_.Pointer()->Get();
 }
 
 GLContext* GLContext::GetRealCurrent() {
   return current_real_context_.Pointer()->Get();
 }
 
 void GLContext::SetCurrent(GLSurface* surface) {
   current_context_.Pointer()->Set(surface ? this : NULL);
   GLSurface::SetCurrent(surface);
+  if (!surface)
+    SetGLApiToNoContext();
 }
 
 GLStateRestorer* GLContext::GetGLStateRestorer() {
   return state_restorer_.get();
 }
 
 void GLContext::SetGLStateRestorer(GLStateRestorer* state_restorer) {
   state_restorer_ = make_scoped_ptr(state_restorer);
 }
 
@@ skipping 38 matching lines @@
     : GLContext(share_group) {}
 
 GLContextReal::~GLContextReal() {}
 
 void GLContextReal::SetCurrent(GLSurface* surface) {
   GLContext::SetCurrent(surface);
   current_real_context_.Pointer()->Set(surface ? this : NULL);
 }
 
 }  // namespace gfx