Restore only modified texture state during virtual context switches

ui/gl/dirty_texture_state.cc

Index: ui/gl/dirty_texture_state.cc
diff --git a/ui/gl/dirty_texture_state.cc b/ui/gl/dirty_texture_state.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1672167a42a6457b1e17a400b2f1d708980cb80b
--- /dev/null
+++ b/ui/gl/dirty_texture_state.cc
@@ -0,0 +1,56 @@
+// Copyright (c) 2013 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/dirty_texture_state.h"
+
+namespace gfx {
+
+const size_t kMaxTextureUnits = 64;
+
+DirtyTextureState::DirtyTextureState()
+    : bindings_(),
+      max_texture_unit_(GL_TEXTURE0) {
+  bindings_.resize(kMaxTextureUnits);
+}
+
+DirtyTextureState::~DirtyTextureState() {
+}
+
+void DirtyTextureState::UpdateMaxTextureUnit(GLenum current_unit) {
+  max_texture_unit_ = std::max(current_unit, max_texture_unit_);
+}
+
+void DirtyTextureState::AddBinding(GLenum current_unit, GLenum target) {
+  int current_unit_index = current_unit - GL_TEXTURE0;
+  DCHECK(current_unit_index >= 0);
+  DCHECK(static_cast<size_t>(current_unit_index) < kMaxTextureUnits);
+  DirtyTextureBindings binding_for_texture = bindings_[current_unit_index];
+
+  switch (target) {
+    case GL_TEXTURE_2D:
+      binding_for_texture.binding_2d = true;
+      break;
+    case GL_TEXTURE_CUBE_MAP:
+      binding_for_texture.binding_cube_map = true;
+      break;
+    case GL_TEXTURE_EXTERNAL_OES:
+      binding_for_texture.binding_external_oes = true;
+      break;
+    case GL_TEXTURE_RECTANGLE_ARB:
+      binding_for_texture.binding_rectangle_arb = true;
+      break;
+    default:
+      NOTREACHED();
+  }
+
+  bindings_[current_unit_index] = binding_for_texture;
+}
+
+void DirtyTextureState::Clear() {
+  max_texture_unit_ = GL_TEXTURE0;
+  bindings_.clear();
+  bindings_.resize(kMaxTextureUnits);
+}
+
+}  // namespace gfx