Don't enable shader extenstions in WebGL 2 when they are already core.

content/test/gpu/gpu_tests/webgl2_conformance_expectations.py

Index: content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
diff --git a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
index 7d33162c05069d40c6dec27983034c219658f225..50054443c3bffe609521c2ca26d5ad224a0e3150 100644
--- a/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
+++ b/content/test/gpu/gpu_tests/webgl2_conformance_expectations.py
@@ -79,14 +79,12 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
 
     self.Fail('conformance2/glsl3/array-complex-indexing.html', bug=483282)
     self.Fail('conformance2/glsl3/forbidden-operators.html', bug=483282)
-    self.Fail('conformance2/extensions/promoted-extensions-in-shaders.html',
-        bug=295792)
     self.Fail('conformance2/samplers/sampler-drawing-test.html', bug=483282)
     self.Fail('conformance2/state/gl-object-get-calls.html', bug=483282)
     # Note that this test fails on ['win', 'intel'] with bug=483282
     self.Fail('conformance2/buffers/uniform-buffers.html', bug=577368)
 
-    # Windows and Mac.
+    # Windows only.
     self.Fail('conformance2/textures/canvas/tex-image-and-sub-image-2d' +
         '-with-canvas-r8-red-unsigned_byte.html',
         ['win'], bug=483282)
@@ -197,7 +195,6 @@ class WebGL2ConformanceExpectations(WebGLConformanceExpectations):
         '-with-webgl-canvas-rgba4-rgba-unsigned_short_4_4_4_4.html',
         ['win'], bug=483282)
 
-    # Windows only.
     self.Skip('deqp/functional/gles3/readpixel.html', ['win'], bug=483282)
     self.Skip('deqp/functional/gles3/texturestatequery.html',
         ['win'], bug=483282)