Use highp for glCopyTexture2D where available

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 263 matching lines @@
       break;
   }
 
   return alphaIndex + targetIndex * 4 + sourceFormatIndex * 4 * NUM_SAMPLERS +
          destFormatIndex * 4 * NUM_SAMPLERS * NUM_S_FORMAT;
 }
 
 const char* kShaderPrecisionPreamble =
     "#ifdef GL_ES\n"
     "precision mediump float;\n"
+    "#ifdef GL_FRAGMENT_PRECISION_HIGH\n"
+    "#define TexCoordPrecision highp\n"
+    "#else\n"
     "#define TexCoordPrecision mediump\n"
+    "#endif\n"
     "#else\n"
     "#define TexCoordPrecision\n"
     "#endif\n";
 
 std::string GetVertexShaderSource(const gl::GLVersionInfo& gl_version_info,
                                   GLenum target) {
   std::string source;
 
   if (gl_version_info.is_es || gl_version_info.IsLowerThanGL(3, 2)) {
     if (gl_version_info.is_es3 && target != GL_TEXTURE_EXTERNAL_OES) {
@@ skipping 834 matching lines @@
   decoder->RestoreTextureUnitBindings(0);
   decoder->RestoreActiveTexture();
   decoder->RestoreProgramBindings();
   decoder->RestoreBufferBindings();
   decoder->RestoreFramebufferBindings();
   decoder->RestoreGlobalState();
 }
 
 }  // namespace gles2
 }  // namespace gpu