Roll third_party/openscreen dependency

Due to openscreen not having a 32-bit build, openscreen previously does
not build in 32-bit, causing issues on 32-bit Chromium build bots. This
patch rolls openscreen to include fixes for this issue.

Change-Id: I11997fabf9822c124e260c228c63445781539b80
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1637523
Commit-Queue: Takumi Fujimoto <takumif@chromium.org>
Reviewed-by: Takumi Fujimoto <takumif@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665311}

DEPS

@@ -1159,7 +1159,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/cisco/openh264' + '@' + '6f26bce0b1c4e8ce0e13332f7c0083788def5fdf',
 
   'src/third_party/openscreen/src':
-    Var('chromium_git') + '/openscreen' + '@' + '6dcfbb6577554933548255799ed7b58bfbfc51fd',
+    Var('chromium_git') + '/openscreen' + '@' + '7bc7f102467b395fbf4963ac34e4844564c783d3',
 
   'src/third_party/ow2_asm': {
       'packages': [