Another manual ANGLE roll

This commit rebased the source paths in the .gni
file from ANGLE's src/ directory to its project root.

The update to third_party/angle2/BUILD.gn does the same.

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: Id814f67bed2dfab11f878544989054e38987a939
Reviewed-on: https://skia-review.googlesource.com/150485
Commit-Queue: Mike Klein <mtklein@google.com>
Commit-Queue: Stephan Altmueller <stephana@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Stephan Altmueller <stephana@google.com>
2 files changed