Update ANGLE

Fixing ANGLE Bugs

Before you commit a WebKit patch that modifies ANGLE, please run Tools/Scripts/update-angle --regenerate-changes. This will update Source/ThirdParty/ANGLE/changes.diff so that people can see the diff from upstream at a glance.

When fixing bugs in ANGLE, please create a new bug on ANGLE's bug tracker and attach the patch applied to WebKit so that changes can eventually be merged upstream instead of maintained locally.

Merging ANGLE from Upstream

To pull in a new revision of ANGLE, run the script Tools/Scripts/update-angle and follow its instructions. This script will attempt to update to a new version of ANGLE without losing WebKit's local changes by performing a git rebase. It also helps to update the CMake build files and ANGLE.plist.