Implement tex{Sub}Image3D taking sub-rectangles of HTMLImageElements.

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 170 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' + '@' + '7516ab728e3ec209f859f30824886fe93ef0bbe4',
+    Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + 'bc2b06dfadf741437dbfdb0ec41c9557770b71e8',
 
   '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' + '@' +  '5c64c01c7ca3780d30f140e54a30088f780ae66a',
 
   'src/third_party/ffmpeg':
     Var('chromium_git') + '/chromium/third_party/ffmpeg.git' + '@' + '3c7a09882102bfd6fecdb9d7296f43a8501db95e',
 
@@ skipping 819 matching lines @@
 ]
 
 recursedeps = [
   # buildtools provides clang_format, libc++, and libc++abi
   'src/buildtools',
   # android_tools manages the NDK.
   'src/third_party/android_tools',
   # ANGLE manages DEPS that it also owns the build files for, such as dEQP.
   ("src/third_party/angle", "DEPS.chromium"),
 ]