Add support for all blendmodes if we have GL_KHR_blend_equation_advanced.

gpu/command_buffer/build_gles2_cmd_buffer.py

Index: gpu/command_buffer/build_gles2_cmd_buffer.py
diff --git a/gpu/command_buffer/build_gles2_cmd_buffer.py b/gpu/command_buffer/build_gles2_cmd_buffer.py
index a6a6323e2f807c18f7a664ee203f08a3541185cc..5747a1dc59b716527644aa43aeaecd8bfa662489 100755
--- a/gpu/command_buffer/build_gles2_cmd_buffer.py
+++ b/gpu/command_buffer/build_gles2_cmd_buffer.py
@@ -1553,6 +1553,12 @@ _FUNCTION_INFO = {
     'type': 'StateSet',
     'state': 'BlendFunc',
   },
+  'BlendBarrierKHR': {
+    'gl_test_func': 'glBlendBarrierKHR',
+    'extension': True,
+    'extension_flag': 'blend_equation_advanced',
+    'client_test': False,
+  },
   'SampleCoverage': {'decoder_func': 'DoSampleCoverage'},
   'StencilFunc': {
     'type': 'StateSetFrontBack',