Add ANGLE as submodule

Bug: b/152028822
Change-Id: I13499a0b13f074d876f6038ab776d5de6e27cd3a
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/47108
Tested-by: Antonio Maiorano <amaiorano@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
diff --git a/.gitmodules b/.gitmodules
index f876631..1b368e5 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -19,3 +19,6 @@
 [submodule "third_party/glslang"]
 	path = third_party/glslang
 	url = https://github.com/KhronosGroup/glslang.git
+[submodule "third_party/angle/angle"]
+	path = third_party/angle/angle
+	url = https://chromium.googlesource.com/angle/angle
diff --git a/third_party/angle/angle b/third_party/angle/angle
new file mode 160000
index 0000000..df5ed61
--- /dev/null
+++ b/third_party/angle/angle
@@ -0,0 +1 @@
+Subproject commit df5ed61ddbcab119b059e6e5bd28a049b726766a