During virtual context switches only restore texture units that have changed from the previous cont…

gpu/command_buffer/service/context_state.cc

Index: gpu/command_buffer/service/context_state.cc
diff --git a/gpu/command_buffer/service/context_state.cc b/gpu/command_buffer/service/context_state.cc
index e8912cfe1625b769dc0047b935c2f098aed31da3..88358ef80f9ba7bcd34bba26b3758251cee36391 100644
--- a/gpu/command_buffer/service/context_state.cc
+++ b/gpu/command_buffer/service/context_state.cc
@@ -26,6 +26,26 @@ void EnableDisable(GLenum pname, bool enable) {
   }
 }
 
+GLuint Get2dServiceId(const TextureUnit& unit) {
+  return unit.bound_texture_2d.get()
+      ? unit.bound_texture_2d->service_id() : 0;
+}
+
+GLuint GetCubeServiceId(const TextureUnit& unit) {
+  return unit.bound_texture_cube_map.get()
+      ? unit.bound_texture_cube_map->service_id() : 0;
+}
+
+GLuint GetOesServiceId(const TextureUnit& unit) {
+  return unit.bound_texture_external_oes.get()
+      ? unit.bound_texture_external_oes->service_id() : 0;
+}
+
+GLuint GetArbServiceId(const TextureUnit& unit) {
+  return unit.bound_texture_rectangle_arb.get()
+      ? unit.bound_texture_rectangle_arb->service_id() : 0;
+}
+
 }  // anonymous namespace.
 
 TextureUnit::TextureUnit()
@@ -47,31 +67,48 @@ ContextState::ContextState(FeatureInfo* feature_info, Logger* logger)
 ContextState::~ContextState() {
 }
 
-void ContextState::RestoreTextureUnitBindings(GLuint unit) const {
+void ContextState::RestoreTextureUnitBindings(
+    GLuint unit, const ContextState* prev_state) const {
   DCHECK_LT(unit, texture_units.size());
   const TextureUnit& texture_unit = texture_units[unit];
-  glActiveTexture(GL_TEXTURE0 + unit);
-  GLuint service_id = texture_unit.bound_texture_2d.get()
-                          ? texture_unit.bound_texture_2d->service_id()
-                          : 0;
-  glBindTexture(GL_TEXTURE_2D, service_id);
-  service_id = texture_unit.bound_texture_cube_map.get()
-                   ? texture_unit.bound_texture_cube_map->service_id()
-                   : 0;
-  glBindTexture(GL_TEXTURE_CUBE_MAP, service_id);
-
-  if (feature_info_->feature_flags().oes_egl_image_external) {
-    service_id = texture_unit.bound_texture_external_oes.get()
-                     ? texture_unit.bound_texture_external_oes->service_id()
-                     : 0;
-    glBindTexture(GL_TEXTURE_EXTERNAL_OES, service_id);
+  GLuint service_id_2d = Get2dServiceId(texture_unit);
+  GLuint service_id_cube = GetCubeServiceId(texture_unit);
+  GLuint service_id_oes = GetOesServiceId(texture_unit);
+  GLuint service_id_arb = GetArbServiceId(texture_unit);
+
+  bool bind_texture_2d = true;
+  bool bind_texture_cube = true;
+  bool bind_texture_oes = feature_info_->feature_flags().oes_egl_image_external;
+  bool bind_texture_arb = feature_info_->feature_flags().arb_texture_rectangle;
+
+  if (prev_state) {
+    const TextureUnit& prev_unit = prev_state->texture_units[unit];
+    bind_texture_2d = service_id_2d != Get2dServiceId(prev_unit);
+    bind_texture_cube = service_id_cube != GetCubeServiceId(prev_unit);
+    bind_texture_oes =
+        bind_texture_oes && service_id_oes != GetOesServiceId(prev_unit);
+    bind_texture_arb =
+        bind_texture_arb && service_id_arb != GetArbServiceId(prev_unit);
+  }
+
+  // Early-out if nothing has changed from the previous state.
+  if (!bind_texture_2d && !bind_texture_cube
+      && !bind_texture_oes && !bind_texture_arb) {
+    return;
   }
 
-  if (feature_info_->feature_flags().arb_texture_rectangle) {
-    service_id = texture_unit.bound_texture_rectangle_arb.get()
-                     ? texture_unit.bound_texture_rectangle_arb->service_id()
-                     : 0;
-    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, service_id);
+  glActiveTexture(GL_TEXTURE0 + unit);
+  if (bind_texture_2d) {
+    glBindTexture(GL_TEXTURE_2D, service_id_2d);
+  }
+  if (bind_texture_cube) {
+    glBindTexture(GL_TEXTURE_CUBE_MAP, service_id_cube);
+  }
+  if (bind_texture_oes) {
+    glBindTexture(GL_TEXTURE_EXTERNAL_OES, service_id_oes);
+  }
+  if (bind_texture_arb) {
+    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, service_id_arb);
   }
 }
 
@@ -101,10 +138,11 @@ void ContextState::RestoreActiveTexture() const {
   glActiveTexture(GL_TEXTURE0 + active_texture_unit);
 }
 
-void ContextState::RestoreAllTextureUnitBindings() const {
+void ContextState::RestoreAllTextureUnitBindings(
+    const ContextState* prev_state) const {
   // Restore Texture state.
   for (size_t ii = 0; ii < texture_units.size(); ++ii) {
-    RestoreTextureUnitBindings(ii);
+    RestoreTextureUnitBindings(ii, prev_state);
   }
   RestoreActiveTexture();
 }
@@ -139,8 +177,8 @@ void ContextState::RestoreGlobalState() const {
   InitState();
 }
 
-void ContextState::RestoreState() const {
-  RestoreAllTextureUnitBindings();
+void ContextState::RestoreState(const ContextState* prev_state) const {
+  RestoreAllTextureUnitBindings(prev_state);
 
   // Restore Attrib State
   // TODO: This if should not be needed. RestoreState is getting called