Add ANGLE support to Viewer on Windows

Change-Id: I97a844b2f289d2518f60a64f94d60551c4530dd4
Reviewed-on: https://skia-review.googlesource.com/35742
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index afa38a1..563f365 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1579,6 +1579,9 @@
           "tools/viewer/sk_app/win/Window_win.cpp",
           "tools/viewer/sk_app/win/main_win.cpp",
         ]
+        if (skia_use_angle) {
+          sources += [ "tools/viewer/sk_app/win/ANGLEWindowContext_win.cpp" ]
+        }
       } else if (is_mac) {
         sources += [
           "tools/viewer/sk_app/mac/GLWindowContext_mac.cpp",
@@ -1618,6 +1621,9 @@
       } else if (is_mac) {
         deps += [ "//third_party/libsdl" ]
       }
+      if (skia_use_angle) {
+        deps += [ "//third_party/angle2" ]
+      }
     }
   }