command_buffer: Fix setting samplers with bound uniforms

gpu/command_buffer/service/program_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_PROGRAM_MANAGER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_PROGRAM_MANAGER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 237 matching lines @@
 
   // Returns the fragment shader output variable color name binding.
   // Returns -1 if |original_name| is not an out variable or error.
   GLint GetFragDataLocation(const std::string& original_name) const;
 
   // Returns the fragment shader output variable color index binding.
   // Returns -1 if |original_name| is not an out variable or error.
   GLint GetFragDataIndex(const std::string& original_name) const;
 
   // Sets the sampler values for a uniform.
-  // This is safe to call for any location. If the location is not
-  // a sampler uniform nothing will happen.
-  // Returns false if fake_location is a sampler and any value
-  // is >= num_texture_units. Returns true otherwise.
+  // This should be called only for valid fake location pointing to
+  // an active uniform.
+  // If the location is not a sampler uniform nothing will happen.
+  // Returns false if fake_location is a sampler and any value is >=
+  // num_texture_units. Returns true otherwise.
   bool SetSamplers(
       GLint num_texture_units, GLint fake_location,
       GLsizei count, const GLint* value);
 
   bool IsDeleted() const {
     return deleted_;
   }
 
   void GetProgramiv(GLenum pname, GLint* params);
 
@@ skipping 351 matching lines @@
 };
 
 inline const FeatureInfo& Program::feature_info() const {
   return *manager_->feature_info_.get();
 }
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_PROGRAM_MANAGER_H_