On OpenGLES backed environment, webgl/1.0.2/conformance/extensions/webgl-debug-shaders.html fails with the same error related with https://bugs.webkit.org/show_bug.cgi?id=149734.
I think the codes that are disabling WEBGL_debug_shaders extension, which are implemented in Extensions3DOpenGL::supportsExtension(), should be moved to Extensions3DOpenGLCommon::supportsExtension() so that the webgl-debug-shaders extension is disabled for both OpenGL and OpenGLES backed systems.
Created attachment 270487 [details]
Comment on attachment 270487 [details]
Attachment 270487 [details] did not pass mac-debug-ews (mac):
New failing tests:
Created attachment 270490 [details]
Archive of layout-test-results from ews112 for mac-yosemite
The attached test failures were seen while running run-webkit-tests on the mac-debug-ews.
Bot: ews112 Port: mac-yosemite Platform: Mac OS X 10.10.5
Created attachment 270529 [details]
Comment on attachment 270529 [details]
Clearing flags on attachment: 270529
Committed r196039: <http://trac.webkit.org/changeset/196039>
All reviewed patches have been landed. Closing bug.