command_buffer: Make inactive bound uniforms reserve the location

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 d688c6941dcbaa34e84afa178a47ca4d50381ea0..5c19cf0bcc503c047f0246707c35150b722dd746 100644
--- a/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
+++ b/gpu/command_buffer/tests/gl_bind_uniform_location_unittest.cc
@@ -268,6 +268,98 @@ TEST_P(BindUniformLocationTest, Compositor) {
 
 }
 
+TEST_P(BindUniformLocationTest, UnusedUniformUpdate) {
+  ASSERT_TRUE(GLTestHelper::HasExtension("GL_CHROMIUM_bind_uniform_location"));
+
+  // clang-format off
+  static const char* kVertexShaderString = SHADER(
+      attribute vec4 a_position;
+      void main() {
+        gl_Position = a_position;
+      }
+  );
+  static const char* kFragmentShaderString = SHADER(
+      precision mediump float;
+      uniform vec4 u_colorA;
+      uniform float u_colorU;
+      uniform vec4 u_colorC;
+      void main() {
+        gl_FragColor = u_colorA + u_colorC;
+      }
+  );
+  // clang-format on
+  const GLint kColorULocation = 1;
+  const GLint kNonexistingLocation = 5;
+  const GLint kUnboundLocation = 6;
+
+  GLuint vertex_shader =
+      GLTestHelper::LoadShader(GL_VERTEX_SHADER, kVertexShaderString);
+  GLuint fragment_shader =
+      GLTestHelper::LoadShader(GL_FRAGMENT_SHADER, kFragmentShaderString);
+  GLuint program = glCreateProgram();
+  glBindUniformLocationCHROMIUM(program, kColorULocation, "u_colorU");
+  // The non-existing uniform should behave like existing, but optimized away
+  // uniform.
+  glBindUniformLocationCHROMIUM(program, kNonexistingLocation, "nonexisting");
+  // Let A and C be assigned automatic locations.
+  glAttachShader(program, vertex_shader);
+  glAttachShader(program, fragment_shader);
+  glLinkProgram(program);
+  GLint linked = 0;
+  glGetProgramiv(program, GL_LINK_STATUS, &linked);
+  EXPECT_EQ(1, linked);
+  glUseProgram(program);
+
+  // No errors on bound locations, since caller does not know
+  // if the driver optimizes them away or not.
+  glUniform1f(kColorULocation, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+
+  // No errors on bound locations of names that do not exist
+  // in the shader. Otherwise it would be inconsistent wrt the
+  // optimization case.
+  glUniform1f(kNonexistingLocation, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+
+  // The above are equal to updating -1.
+  glUniform1f(-1, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+
+  // No errors when updating with other type either.
+  // The type can not be known with the non-existing case.
+  glUniform2f(kColorULocation, 0.25f, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+  glUniform2f(kNonexistingLocation, 0.25f, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+  glUniform2f(-1, 0.25f, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_NO_ERROR), glGetError());
+
+  // Ensure that driver or ANGLE has optimized the variable
+  // away and the test tests what it is supposed to.
+  EXPECT_EQ(-1, glGetUniformLocation(program, "u_colorU"));
+
+  // The bound location gets marked as used and the driver
+  // does not allocate other variables to that location.
+  EXPECT_NE(kColorULocation, glGetUniformLocation(program, "u_colorA"));
+  EXPECT_NE(kColorULocation, glGetUniformLocation(program, "u_colorC"));
+  EXPECT_NE(kNonexistingLocation, glGetUniformLocation(program, "u_colorA"));
+  EXPECT_NE(kNonexistingLocation, glGetUniformLocation(program, "u_colorC"));
+
+  // Unintuitive: while specifying value works, getting the value does not.
+  GLfloat get_result = 0.0f;
+  glGetUniformfv(program, kColorULocation, &get_result);
+  EXPECT_EQ(static_cast<GLenum>(GL_INVALID_OPERATION), glGetError());
+  glGetUniformfv(program, kNonexistingLocation, &get_result);
+  EXPECT_EQ(static_cast<GLenum>(GL_INVALID_OPERATION), glGetError());
+  glGetUniformfv(program, -1, &get_result);
+  EXPECT_EQ(static_cast<GLenum>(GL_INVALID_OPERATION), glGetError());
+
+  // Updating an unbound, non-existing location still causes
+  // an error.
+  glUniform1f(kUnboundLocation, 0.25f);
+  EXPECT_EQ(static_cast<GLenum>(GL_INVALID_OPERATION), glGetError());
+}
+
 INSTANTIATE_TEST_CASE_P(WithAndWithoutShaderNameMapping,
                         BindUniformLocationTest,
                         ::testing::Bool());