roll ANGLE w/ GN update

ANGLE switched their .gypi files to .gni files this commit,
so we need to make a small tweak to update our ANGLE build.

This removes the last use of gypi_to_gn.py, and in turn gn_helpers.py.

CQ_INCLUDE_TRYBOTS=skia.primary:Build-Debian9-Clang-x86_64-Release-ANGLE;skia.primary:Perf-Win10-Clang-AlphaR2-GPU-RadeonR9M470X-x86_64-Debug-All-ANGLE;skia.primary:Perf-Win10-Clang-NUC5i7RYH-GPU-IntelIris6100-x86_64-Debug-All-ANGLE;skia.primary:Perf-Win10-Clang-NUC6i5SYK-GPU-IntelIris540-x86_64-Debug-All-ANGLE;skia.primary:Perf-Win10-Clang-NUCD34010WYKH-GPU-IntelHD4400-x86_64-Debug-All-ANGLE;skia.primary:Perf-Win10-Clang-ShuttleC-GPU-GTX960-x86_64-Debug-All-ANGLE;skia.primary:Test-Win10-Clang-AlphaR2-GPU-RadeonR9M470X-x86_64-Debug-All-ANGLE;skia.primary:Test-Win10-Clang-NUC6i5SYK-GPU-IntelIris540-x86_64-Debug-All-ANGLE;skia.primary:Test-Win10-Clang-NUCD34010WYKH-GPU-IntelHD4400-x86_64-Debug-All-ANGLE;skia.primary:Test-Win10-Clang-ShuttleC-GPU-GTX960-x86_64-Debug-All-ANGLE


Change-Id: I76c8a667e7c5c27dc4cd18ba0d932bfc2de38cf9
Reviewed-on: https://skia-review.googlesource.com/150541
Reviewed-by: Stephan Altmueller <stephana@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/DEPS b/DEPS
index 4d25609..e296b00 100644
--- a/DEPS
+++ b/DEPS
@@ -7,7 +7,7 @@
 deps = {
   "buildtools"                            : "https://chromium.googlesource.com/chromium/buildtools.git@505de88083136eefd056e5ee4ca0f01fe9b33de8",
   "common"                                : "https://skia.googlesource.com/common.git@9737551d7a52c3db3262db5856e6bcd62c462b92",
-  "third_party/externals/angle2"          : "https://chromium.googlesource.com/angle/angle.git@1e1b731a98955fb4fe9cd5a17887e2abcdb283d5",
+  "third_party/externals/angle2"          : "https://chromium.googlesource.com/angle/angle.git@ddc41208c15ffd9aae99e3ac6c9d59a09df914d9",
   "third_party/externals/dng_sdk"         : "https://android.googlesource.com/platform/external/dng_sdk.git@96443b262250c390b0caefbf3eed8463ba35ecae",
   "third_party/externals/egl-registry"    : "https://skia.googlesource.com/external/github.com/KhronosGroup/EGL-Registry@a0bca08de07c7d7651047bedc0b653cfaaa4f2ae",
   "third_party/externals/expat"           : "https://android.googlesource.com/platform/external/expat.git@android-6.0.1_r55",