command_buffer: Fix setting samplers with bound uniforms

gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc

Index: gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
diff --git a/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc b/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
index 3afb5f716ad1e0133f42562ba5f64116af8511dc..8856500348f0dca67f3b8cffb7257480e8111999 100644
--- a/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
+++ b/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
@@ -361,6 +361,47 @@ TEST_P(BindUniformLocationTest, UnusedUniformUpdate) {
   EXPECT_EQ(static_cast<GLenum>(GL_INVALID_OPERATION), glGetError());
 }
 
+// Test for a bug where using a sampler caused GL error if the program had
+// uniforms that were optimized away by the driver. This was only a problem with
+// glBindUniformLocationCHROMIUM implementation. This could be reproed by
+// binding the sampler to a location higher than the amount of active uniforms.
+TEST_P(BindUniformLocationTest, UseSamplerWhenUnusedUniforms) {
+  enum {
+    kTexLocation = 54
+  };
+  // clang-format off
+  static const char* vertexShaderString = SHADER(
+      void main() {
+        gl_Position = vec4(0);
+      }
+  );
+  static const char* fragmentShaderString = SHADER(
+      uniform sampler2D tex;
+      void main() {
+        gl_FragColor = texture2D(tex, vec2(1));
+      }
+  );
+  // clang-format on
+  GLuint vs = GLTestHelper::CompileShader(GL_VERTEX_SHADER, vertexShaderString);
+  GLuint fs = GLTestHelper::CompileShader(GL_FRAGMENT_SHADER,
+                                          fragmentShaderString);
+
+  GLuint program = glCreateProgram();
+  glBindUniformLocationCHROMIUM(program, kTexLocation, "tex");
+
+  glAttachShader(program, vs);
+  glAttachShader(program, fs);
+
+  glLinkProgram(program);
+
+  GLint linked = 0;
+  glGetProgramiv(program, GL_LINK_STATUS, &linked);
+  EXPECT_NE(0, linked);
+  glUseProgram(program);
+  glUniform1i(kTexLocation, 0);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+}
+
 INSTANTIATE_TEST_CASE_P(WithAndWithoutShaderNameMapping,
                         BindUniformLocationTest,
                         ::testing::Bool());