Reland of Select correct copy method for DoCopySubTexture

gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.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 "gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 778 matching lines @@
     GLsizei width,
     GLsizei height,
     GLsizei dest_width,
     GLsizei dest_height,
     GLsizei source_width,
     GLsizei source_height,
     bool flip_y,
     bool premultiply_alpha,
     bool unpremultiply_alpha,
     CopyTextureMethod method) {
-  bool use_gl_copy_tex_sub_image_2d = true;
-#if defined(OS_CHROMEOS) && defined(ARCH_CPU_X86_FAMILY)
-  // glDrawArrays is faster than glCopyTexSubImage2D on IA Mesa driver,
-  // although opposite in Android.
-  // TODO(dshwang): After Mesa fixes this issue, remove this hack.
-  // https://bugs.freedesktop.org/show_bug.cgi?id=98478 crbug.com/535198
-  use_gl_copy_tex_sub_image_2d = false;
-#endif
   bool premultiply_alpha_change = premultiply_alpha ^ unpremultiply_alpha;
   GLenum dest_binding_target =
       gpu::gles2::GLES2Util::GLFaceTargetToTextureTarget(dest_target);
 
   // GL_TEXTURE_RECTANGLE_ARB on FBO is supported by OpenGL, not GLES2,
   // so restrict this to GL_TEXTURE_2D and GL_TEXTURE_CUBE_MAP.
-  if (use_gl_copy_tex_sub_image_2d && source_target == GL_TEXTURE_2D &&
+  if (source_target == GL_TEXTURE_2D &&
       (dest_binding_target == GL_TEXTURE_2D ||
        dest_binding_target == GL_TEXTURE_CUBE_MAP) &&
       !flip_y && !premultiply_alpha_change && method == DIRECT_COPY) {
     DoCopyTexSubImage2D(decoder, source_target, source_id, source_level,
                         dest_target, dest_id, dest_level, xoffset, yoffset, x,
                         y, width, height, framebuffer_);
     return;
   }
 
   // Draw to level 0 of an intermediate GL_TEXTURE_2D texture.
@@ skipping 331 matching lines @@
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
 }
 
 }  // namespace gles2
 }  // namespace gpu