Emulate TEXTURE_IMMUTABLE_LEVELS on GL lower than 4.2

gpu/command_buffer/service/texture_manager.h

 // 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.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_TEXTURE_MANAGER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_TEXTURE_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 228 matching lines @@
   }
 
   void SetImmutable(bool immutable) {
     immutable_ = immutable;
   }
 
   bool IsImmutable() const {
     return immutable_;
   }
 
+  // Return 0 if it's not immutable.
+  GLint GetImmutableLevels() const;
+
   // Get the cleared rectangle for a particular level. Returns an empty
   // rectangle if level does not exist.
   gfx::Rect GetLevelClearedRect(GLenum target, GLint level) const;
 
   // Whether a particular level/face is cleared.
   bool IsLevelCleared(GLenum target, GLint level) const;
   // Whether a particular level/face is partially cleared.
   bool IsLevelPartiallyCleared(GLenum target, GLint level) const;
 
   // Whether the texture has been defined
@@ skipping 879 matching lines @@
  private:
   DecoderTextureState* texture_state_;
   base::TimeTicks begin_time_;
   DISALLOW_COPY_AND_ASSIGN(ScopedTextureUploadTimer);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_TEXTURE_MANAGER_H_