Bug 1087650 - Mark failing tests on B2G.

dom/canvas/test/webgl-mochitest.ini

@@ -6,11 +6,13 @@ support-files =
   webgl-mochitest/webgl-util.js
 
 [webgl-mochitest/test_backbuffer_channels.html]
+fail-if = (os == 'b2g')
 [webgl-mochitest/test_depth_readpixels.html]
 [webgl-mochitest/test_draw.html]
 [webgl-mochitest/test_fb_param.html]
 [webgl-mochitest/test_fb_param_crash.html]
 [webgl-mochitest/test_hidden_alpha.html]
+fail-if = (os == 'b2g')
 [webgl-mochitest/test_highp_fs.html]
 [webgl-mochitest/test_no_arr_points.html]
 skip-if = android_version == '10' #Android 2.3 aws only; bug 1030942