Roll WebGL 46ec84c..a7fa4b5 and update webgl expectation

DEPS

 # This file is used to manage the dependencies of the Chromium src repo. It is
 # used by gclient to determine what version of each dependency to check out, and
 # where.
 #
 # For more information, please refer to the official documentation:
 #   https://sites.google.com/a/chromium.org/dev/developers/how-tos/get-the-code
 #
 # When adding a new dependency, please update the top-level .gitignore file
 # to list the dependency's destination directory.
 #
@@ skipping 160 matching lines @@
   'src/chrome/test/data/perf/canvas_bench':
    Var('chromium_git') + '/chromium/canvas_bench.git' + '@' + 'a7b40ea5ae0239517d78845a5fc9b12976bfc732',
 
   'src/chrome/test/data/perf/frame_rate/content':
    Var('chromium_git') + '/chromium/frame_rate/content.git' + '@' + 'c10272c88463efeef6bb19c9ec07c42bc8fe22b9',
 
   'src/third_party/bidichecker':
     Var('chromium_git') + '/external/bidichecker/lib.git' + '@' + '97f2aa645b74c28c57eca56992235c79850fa9e0',
 
   'src/third_party/webgl/src':
-   Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '46ec84c307584e6ffebc327958d56d89c36e6c27',
+   Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + 'a7fa4b5842abc94174f07e2728917c298f35b08e',
 
   'src/third_party/webdriver/pylib':
     Var('chromium_git') + '/external/selenium/py.git' + '@' + '5fd78261a75fe08d27ca4835fb6c5ce4b42275bd',
 
   'src/third_party/libvpx/source/libvpx':
    Var('chromium_git') + '/webm/libvpx.git' + '@' +  '82070ae9393b1e79559d81fcf1aa89c2e4aa58ee',
 
   'src/third_party/ffmpeg':
    Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + '4e878f7f64d7a9f06ba076d0a2611d7f8b33d793',
 
@@ skipping 781 matching lines @@
     'name': 'doclava',
     'pattern': '.',
     'action': ['python',
                'src/build/android/download_doclava.py',
     ],
   },
 ]
 
 # ANGLE manages DEPS that it also owns the build files for, such as dEQP.
 recursedeps = [("src/third_party/angle", "DEPS.chromium")]