GLVersionInfo: for ES3 check for sampler array indexing

ui/gl/gl_version_info.cc

 // Copyright 2014 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/gl_version_info.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_tokenizer.h"
 #include "base/strings/string_util.h"
@@ skipping 72 matching lines @@
   // Don't try supporting ES3 on ES2, or desktop before 3.2 because there are no
   // extension that allow querying for GL_MAX_FRAGMENT_INPUT_COMPONENTS
   if (is_es || !IsAtLeastGL(3, 2)) {
     return false;
   }
 
   bool has_shader_packing = has_extension("GL_ARB_shading_bit_packing") ||
                             has_extension("GL_ARB_shader_bit_encoding");
   bool has_transform_feedback =
       IsAtLeastGL(4, 0) || has_extension("GL_ARB_transform_feedback2");
+  // Technically this is required for ES2 as well, but some drivers silently
+  // support it, without the required extensions. To avoid breaking WebGL for
+  // some users, only require detectable support for ES3.
+  bool has_sampler_indexing = IsAtLeastGL(4, 0) || IsAtLeastGLES(2, 0) ||

[Zhenyao Mo, 2016/06/28 21:43:26]

nit: IsAtLeastGLES(2, 0) can be is_es, which is clearer.

+                              has_extension("GL_ARB_gpu_shader5");
   bool has_samplers =
       IsAtLeastGL(3, 3) || has_extension("GL_ARB_sampler_object");
   bool has_swizzle = IsAtLeastGL(3, 3) ||
                      has_extension("GL_ARB_texture_swizzle") ||
                      has_extension("GL_EXT_texture_swizzle");
   bool has_attrib_location =
       IsAtLeastGL(3, 3) || has_extension("GL_ARB_explicit_attrib_location");
 
   // TODO(cwallez) check for texture related extensions. See crbug.com/623577
 
-  return has_shader_packing && has_transform_feedback && has_samplers &&
-         has_swizzle && has_attrib_location;
+  return has_shader_packing && has_transform_feedback && has_sampler_indexing &&
+         has_samplers && has_swizzle && has_attrib_location;
 }
 
 void GLVersionInfo::ParseVersionString(const char* version_str,
                                        unsigned* major_version,
                                        unsigned* minor_version,
                                        bool* is_es,
                                        bool* is_es2,
                                        bool* is_es3) {
   // Make sure the outputs are always initialized.
   *major_version = 0;
@@ skipping 18 matching lines @@
     }
   }
   if (*is_es && *major_version == 2)
     *is_es2 = true;
   if (*is_es && *major_version == 3)
     *is_es3 = true;
   DCHECK(major_version != 0);
 }
 
 }  // namespace gl